by John Drewienkiewicz
This is an improved version of the talk delivered at the ACWRT Annual Lunch at the Royal Overseas League, London, on 2 April 2004.
Combat and Field Engineering in the Civil War is a not a well documented subject, with little in the way of source material. Unlike the cavalry and artillery arms, there is no readily accessible book dedicated to the tale of each side's exploits in the area. Yet the engineering problems of the Civil War were very real, the more so because so much of the War was conducted in areas of sparsely populated practically uncharted wilderness.
In this respect the Civil War was nothing like most of the Napoleonic Wars, in whose history the leaders of the armies were well versed. Where it was like those earlier wars, there appears to have been little ability to learn the lessons. The article can be briefly described as "Digging and Bridging", but in fact there is more to it than this; it will be argued that neglect of engineering foresight was a fatal factor for the South.
What are military engineers?
Today it is said by instinct that military engineers have three interconnected roles: to enable armies: "to live, move and fight". In doing this they are needed throughout the battlefield, from the front to the back. But in 1861 the accepted role of engineers was to help the army to live and fight, but without much emphasis placed on enabling or facilitating movement. At this time there was a US Corps of Engineer officers. All cadets at West Point received a four year education that was heavily biased in engineering. Those who did best went into the Engineer Corps, such as Robert E Lee of course. The not so clever went into the infantry. But it follows from their education that all West Point educated officers should have been thoroughly sensitised to engineering problems.
US Military Engineers in 1860
The engineer effort of the Pre-War US Army was devoted to building formidable masonry forts to protect the approaches to ports and harbours. This was because the previous war that involved Americans fighting at home had been in 1812, when the eastern seaboard of the USA had been proven to be highly vulnerable to amphibious raiding by the Royal Navy. Thus it was that Lee had spent many years on fort construction, with a workforce of skilled civilian artisans, who worked for years on these guards at the entrances to USA. There were a handful of companies of engineers, with soldier artisans as well as officers; these artisans were skilled in the "biblical" trades of carpentry, masonry and waterworks, but they were the exception. They were brought together early in the War as the Regular Engineer Battalion of Sappers and Miners.
The Outbreak of War
Since the main thing the engineers did was construct forts, and since it was going to be a short war, no new ones would be needed. Again, while barracks would have been nice, there was no time, so it was tents for almost everyone. Once the first winter of the war arrived the armies did go into winter quarters, but that was achieved by letting the soldiers construct their own shanties, using the considerable DIY skills that existed in the armies. One final area where engineers should have had a role was in water supply, but this was generally neglected, with the result that lack of water was often a problem. Think of the defenders of Vicksburg, without enough wells dug; think of the attackers of Little Round Top who had detached around 10%of their strength to fill up the empty water canteens in the midst of battle because they were fainting from thirst.
There were many ways of enabling movement in 1860. Among them were maps, roads, railways, sawmills, fords, bridges, ferries, ports and harbours. It can be argued that of these, maps are the most important; because with accurate maps the movement of troops can be accurately planned so that units and formations arrive where they are wanted, when they are wanted. The story of Stonewall Jackson telling Jedediah Hotchkiss to "make him a map of the Valley", so that he knew all the back roads and short cuts, is very well known. But there are far more examples of battles being fought without the benefit of good maps. Grant said at the start of his moves against Vicksburg that: "Rosecrans, when he left for his new assignment, had taken the best area maps".
The history of the American Civil War is littered with moments when the movement of whole Corps was dependent upon the local knowledge of some young lad acting as a guide. In an advance it is expected that demolitions will have been carried out, and roads may need improvement, so a body of troops equipped to improve routes would have greatly speeded things up. But it seldom happened. Again, both sides recognised the value of railways as a means of resupply and of rapid troop movement, and both sides therefore saw the value of cutting the other side's railway. But the ability to repair railways quickly was not universally regarded as necessary. With wood as the most available construction material, sawmills had a strategic value, but there was no recognised need to invent a mobile sawmill so as to be able to cut timber at will. Everywhere that a road crossed a river there was usually a need for a bridge, capable of carrying light loads such as marching troops, guns and wagons, or railway bridges capable of bearing the 50-80 tons of a train with 20 loaded boxcars. All of this was vital and all was ignored in the early days of the war.
Helping an Army to fight
As stated above, enabling rapid movement was not seen as a priority at first. Where permanent fortifications existed they were seized and were generally held. In the south the forts were Union toeholds, and offered possible avenues of approach for later Union moves.
Once the South had bombarded Fort Sumter into submission it was used as the centre of the fixed defences of Charleston, which Beauregard improved considerably, so that Charleston's seaward defences held out against many attacks. Siege warfare was a factor, and several Union officers had been observers in the Crimean War, and thus had seen of the defensive power of permanent defences as well as how to carry out a formal siege operation. So it was that, in the Peninsular, Magruder was able to convince McClellan that he faced such powerful defences that a formal siege would be necessary.
McClellan settled down to a siege and waited for heavy siege artillery to be brought up, which cost him a month and gave the South time to rush reinforcements to Magruder. Both sides were aware of the power of water; Magruder's position was made more defensible, and his line shortened, by the use of flooding to protect his vulnerable flanks. But McClellan only used the shipping that had transported his army to the Peninsula as a logistic movement asset, and did not use it to bypass the land-based defences being constructed by the Confederates.
The infrastructure was decidedly unlike that of Europe. While there were railways, they were not a proper interconnected network. There was not a common gauge, which made movement over strategic distances more time-consuming than it might have been. That said, they were certainly essential for logistics, especially in the areas where the rivers flowed the wrong way, which was almost everywhere.
The landscape was similarly different to that of Europe. The towns were small and far apart, with seriously big rivers separating them. In the spring the snow melt made the rivers impassable for weeks at a time, and rivers could rise rapidly and without warning, as the Potomac did to the rear of Lee at Falling Waters after Gettysburg. The rivers usually burst their banks in the spring, and the further west you went, the worse it got.
The Mississippi was not bridged in the Vicksburg area until the 1930s; even the tributaries of the Mississippi were formidable in their own right. The Mississippi was also notorious for changing its channel from time to time in the spring. In all this there were few roads that deserved the name and which were capable of supporting the movement of artillery and wagons in the quantities that were needed. In the east the situation was better, with some plank roads and the occasional hard surfaced road, such as the Chambersburg Pike. But they were the exceptions. The space in between was covered by trees except where farmers had cleared the land of trees and rocks so that the land would bear crops. But generally the farms were islands of clear space in a landscape of trees.
Trees are a real impediment to close order drill of the sort that the armies of 1861 learned. Command and control in the pre-radio era was largely by hand and flag signal, or at best by bugle call. This is infinitely easier to accomplish in flat, open ground, so battles tended to occur where there were fewer trees. In the Eastern Theatre there was rarely less than 50% of the terrain covered by trees, while the further west one went, the more infrequent clearings became. In May 1863 Brigadier General GK Warren, then the Chief of Topographical Engineers of the Army of the Potomac, reported: "(From the slashings in front of the fortifications of Washington to those of Richmond)..it is a region whose characteristic is a dense forest of oak or pine, with occasional clearings, rarely extensive enough to prevent the riflemen concealed in one border from shooting across to the other side, a forest which with but few exceptions, required the axemen to precede the artillery."
On the Mississippi flood plain the problem was even worse, since the flat areas there were waterlogged, and trees are notoriously adept at growing vigorously when their roots are in water.
Proportions of Engineers in an Army
At the start of the War every person with any previous military experience was given the task of training the volunteers as infantry and artillery. Those volunteers with equestrian skills were generally selected for training as cavalry, but hardly any thought was given to the raising and training of specialist engineer units, using the skills that many civilian tradesmen had. The received wisdom was that whenever engineering skills were needed there would always be enough appropriately skilled individuals in any unit to be able to construct any field structure, given time and tools. One of the more sensible things that Hooker did, and he actually did quite a lot of sensible things, was to acquire and keep available entrenching tools, shovels, picks and axes, 20,000 tools all told.
This happened in late February 1863. But when engineering was executed by temporarily assigned troops it meant that the unit was tackling each task for the first time, which inevitably meant that they did not care for the tools, they did not task organise, nor did they invent prefabricated solutions. All in all they did not improve with time and experience. The largest dedicated engineer formation that is mentioned in the Official Record is the Union Engineer Brigade. This appears to have been a two regiment strong formation, around 1400 strong. As an Army of the Potomac asset, it was not assigned to any of the corps of the army, but was held centrally, to be deployed by the Army staff. By way of comparison, the artillery was generally allocated to the corps level of command, with a substantial reserve being held at army level. Similarly, the cavalry amounted to around 10% of most armies. Remaining with the theme of specialised units, in the Western Theatre Grant had in his army the "Engineer Regiment of the West". This unit appears to have spent most of the Vicksburg Campaign on the west bank of the Mississippi improving roads and tracks for the logistic trains.
Overall, the Union employed something less than 1% of its strength as engineer troops. The Confederacy devoted even fewer resources to dedicated engineer units. The need for a standing, permanently assigned engineer unit was only agreed by the South after the near disaster at Falling Waters in the summer of 1863. Even then, the Confederacy never assigned more than 1% of its manpower to employment as engineers in the East, and there is little evidence of any dedicated engineer units in the West. In contrast to this severe lack of engineers was the superfluity of artillery. It is of note that there were very few, if any, occasions when it was possible to bring it all to bear, because either the crowded terrain, or the shoddy command and control, or both, did not allow for it. Artillery was always a large proportion of any army, almost always 10% of the overall strength. It can be argued that had just one artillery unit in ten been reenrolled as engineers, this move would have provided the men, wagons and horses to more than double the available specialist engineers. As it was, the total proportion of engineers never reached even 2% of the total strength of any Civil war Army.
Early days of the war
At first both sides raced to raise infantry, artillery and cavalry units. With a short war apparently in prospect there appeared to be no need for engineers. In the days preceding First Bull Run the retreating Confederates felled trees across the roads, which severely hampered the advancing Union troops. But that aside, the battle was an engineering non-event. Neither side entrenched properly; neither side really knew the ground, and both sides used the topography "as found", without attempting to alter it in any way. A year on, in the Peninsular/Seven Days Campaign, the Union still had no prefabricated engineer resources permanently assigned to the field army to enable them to move quickly to overcome difficult terrain. Thus they had to construct ramshackle bridges such as the "Grapevine Bridge" to cross rivers that they should have known bisected their positions. While the Confederates did buy valuable time by the construction of substantial field defences, their lack of accurate road maps prevented them from putting together coordinated attacks. There were several golden opportunities to maneuver onto the exposed flanks of the Union Army, but they all foundered due to the lack of a clear idea of the road network east of Richmond. In short, although the action was within earshot of the bells of the churches of Richmond, the Confederate High Command did not know where roads intersected, if indeed they did intersect. This lack of maps became a battle-losing factor, resulting in uncoordinated frontal attacks when coordinated converging attacks were ordered.
Three case studies will be used to illustrate where engineers were used, and where the engineer skills were, or were not, sufficient. The case studies are Fredericksburg, specifically examining the Union use of its pontoon bridging, Vicksburg, where classical siege warfare was the order of the day, and the extraordinary measures taken by the Union to repair railroads as they advanced. One case study is in the east, one in the west, and one was applied to both theatres.
The Fredericksburg Campaign took place in the early winter of 1862, and was the first time that specialist engineers were used in an assault. Burnside decided to cross the Rappahannock by means of pontoon bridges, constructed by specialist engineer units. There were fords available upstream from Fredericksburg, but Burnside was reluctant to use them in case the water level rose suddenly and cut off part of his army from the main body. Unfortunately what began as a good plan, of outflanking a smaller enemy force, provided the plan was put into effect quickly, was so delayed that it turned into an opposed frontal assault against an enemy in prepared positions. A major factor in the delay was the time it took to concentrate, fully equip and move up the pontoon bridging. The pontoon bridge unit was ordered to move from where it was using the bridging at Harper's Ferry to Washington on 6th November, and took more than a week to get there. There was then a delay of several days while the onward movement was prepared, with the move south from Washington beginning only on 19th November.
The bridge train arrived in the Fredericksburg area on 27th November, having taken eight days to move the 50 miles, using a mixture of road movement and of floating the pontoons to where they were needed. There was then further delay while Burnside issued orders and adjusted the position of the various elements of his army, before the assault river crossing was launched on 11th December. What would have been an unopposed crossing at first, and a lightly opposed crossing in late November, was a crossing in the face of a well-prepared and entrenched enemy when it was eventually carried out. Meanwhile, on the Confederate side, Longstreet ordered the already good defensive position that he occupied to be improved.
Located so as to dominate the roads and open ground, the fieldworks had been designed for use by a skeleton force which could hold them against a surprise attack until reserves arrived. The innovation was the traversed trench. Longstreet's engineers had broken the long ditches into quite short, squad-sized rifle trenches, staggered in depth, disposed for mutual support, and connected by traverses which could be used against flank attacks and afforded solid protection from all but direct artillery hits.
The Rappahannock at Fredericksburg is around 400 foot wide, a formidable wet gap at any time. The Union assault crossing plan called for the construction of six bridges, three opposite the town inside direct rifle fire range, and three well south of the town, well out of direct range of the nearest Confederate positions.
Bridge construction began at 3am and when day broke there was a light morning mist; this reduced visibility enough to hamper the Union supporting artillery, but not so thick that it made the bridge builders invisible to enemy sharp-shooters in the outskirts of the town. The engineers building the northern bridges were exposed to the fire of the Confederate pickets located close to the river. The engineers took substantial casualties and were forced to abandon their work. After a delay of around four hours the situation was retrieved by some valiant infantry crossing using the pontoons as boats (but which were paddled by the engineers); they established a bridgehead and drove the Confederates back from the bank of the river. Overall, the three bridges that were not subjected to fire were completed in eight hours, while the three opposite the town were completed in twelve hours. The engineer challenges did not finish there, as there was one further obstacle for the Union to overcome, of which they were unaware. Between the town and the Confederate position there was a man-made water channel, designed to drive a mill. This spillway was 30 feet wide and 6 feet deep, and was bridged in only three places. The obstacle was undetected by the Union attackers until after the attack had been launched. The effect of the spillway was to slow down and disrupt the attack, causing bunching at the crossing points and providing a dense target for artillery fire. The lengthening of the time during which the attackers were exposed to fire was certainly a key factor in the excessive casualties suffered by the attackers; while the defenders' entrenchments substantially reduced the casualties they suffered. The overall exchange rate, some 9,000 Union casualties inflicted for the loss of just 2,000 Confederates, was an extremely vivid illustration of the power of a well-protected defence. It was to influence Longstreet deeply and certainly contributed to his strong conviction that the Confederates should maneuver into a defensive position at Gettysburg so that the Union would be compelled to do the attacking.
The Union side of the Vicksburg Campaign can be seen in hindsight as a relentless advance, with many successful improvisations. But at the time any one of the improvisations, had it not worked, could have led to the campaign dragging on for many more months, possibly into the winter of 1863/64. Vicksburg occupied a naturally strong position, with forts dominating river traffic on the River Mississippi. In the six months between November 1862 and May 1863 Grant attempted to get to within assaulting distance of Vicksburg using the eastern bank of the river. Eventually he switched his efforts to the low-lying and flooded west bank of the river. In doing so he committed the only engineer unit he appears to have had to constructing bridges and improving tracks on the western flood plain of the Mississippi. His crossing of the river, well to the south of the Confederate defences, was a major operation. The river was around half a mile wide and the current was extremely swift. The combination of width and current speed meant that a pontoon bridge was out of the question, so the crossing had to be a Navy-run assault landing. The poor infrastructure of the whole region hindered both the attacker and the defender. Until Grant had a foothold on the eastern bank of the river, the difficulty of the terrain favoured the defender. However, once Grant was across the river, he was able to build up his forces faster than the Confederates could assemble forces to attack the incursion. Moreover, the decision by the Confederate defenders of Vicksburg to construct defences on the landward side of the city committed the defenders to garrisoning the defences. Thus, when Pemberton decided to take to the field to confront Grant, he divided his forces, leaving two divisions, some 40% of his strength, holding Vicksburg. His decision on where to offer battle was not assisted by a better knowledge of the ground than Grant had. Pemberton does not appear to have made much effort to map the approaches to Vicksburg in the months that Grant was hovering in the vicinity. Once Grant had made his successful landfall he was able to find out where all the roads went to from sympathetic inhabitants (1), and succeeded in keeping a substantial river, the Big Black, on his open flank between the Union forces and the Vicksburg defenders. His successful battle at Champion Hill was innocent of any engineer effort on either side, and both sides were equally ignorant of the terrain. Grant only seems to have become aware of the formidable nature of the Vicksburg defences when he arrived in front of them. He gambled that the defenders were still disorganised after their retreat, and ordered two assaults against the defences in quick succession. Both assaults bounced off, with the defender inflicting far more casualties than they suffered (2).Grant then was forced to resort to a formal siege, for which he was not well prepared.
Indeed, he was extremely short of engineer officers, and appears not to have had any engineer units. Hence the siege techniques had to be learned from scratch, but luckily for the Union their Western units contained a lot of skilled workmen, and the requisites for a siege were rapidly improvised. Gabions were constructed to reinforce approach trenches, sap rollers were put together, scaling ladders were built, and miners came forward to dig mines under the Confederate strong points. The descriptions of the siege operations are very reminiscent of siege operations by the British in Spain more than 50 years earlier. The siege of Vicksburg was a testament to the native wit of Grant's rugged army, but it was achieved despite the lack of engineer units, and the conclusion could well have been hastened with some dedicated engineer assets. All in all the campaigns in the west are a triumph of improvisation.
3. Repair of Railroads by the Union
Both sides used railways strategically for rapid movement of large forces, and for logistics. Indeed, both sides tended to be very dependent upon the railways for supply of the large armies that were often operating in uninhabited and barren areas. This dependence made the railways a prime target for raids, and both sides became increasingly adept at wrecking the railways of the other side. However, the Confederates were not able to restore wrecked lines to use rapidly. On the other hand, the Union devoted considerable resources to railway repair, so that they were less affected by the temporary loss of a railway line. All in all, the raids damaged the Confederates more than the Union. This was as true in the Western theatre as in the East. In both theatres the Union found a skilled railroad engineer and made good use of his talents. In the East the individual was Herman Haupt, a West Point graduate who had resigned from the Army when still a young man and had been working before the War on railroad construction as a civilian. In the West it was Greville Dodge, a civilian railroad engineer with no formal military background, but who rapidly rose to command an infantry division.
Herman Haupt came to the fore when he was appointed to repair the wrecked railroad behind the advancing Union forces in April 1862. The railway in question was the Richmond and Fredericksburg, and it was needed especially badly because it ran through an area which had been foraged bare by the Confederates in the months when they held the line of the Bull Run. Haupt was assigned some assistants and three companies of infantry. He set to repairing the track immediately. Within a week he had re-laid three miles of sleepers and track. Two days later he had bridged the Ackakeek creek with a 150-foot long bridge. His great challenge was to bridge the Potomac Creek, which was in a far more formidable gorge. In 9 days he had constructed the bridge, some 400 feet long and 100 feet high using timber cut locally.
Twelve days after arriving at the bridge site the track had been laid and the bridge had been crossed by the first train. It was later described by Lincoln as being "nothing but beanpoles and cornstalks".
Greville Dodge was not offered civilian assistants in the West, but instead Grant simply gave him the task of repairing the Central Alabama Railroad with just the resources of his infantry division. As such, Dodge faced a situation where the railroad was completely destroyed, bridges burned, all rails lifted and twisted. The division had only its own entrenching tools; in addition it had to live off the land and provide its own protection. Dodge brought together all those with civilian metal working experience. They found blacksmiths' shops and sawmills and dismantled them and moved them to the railway line. The first things the metal workers made were the tools they would need to carry out the railway repairs. Only then could they set about the repair of the line. Forty days after they had been given the task they reported that the line was open, with 102 miles of track replaced, and with 182 bridges and culverts constructed. Perhaps this feat exemplifies the more practical and pragmatic approach of the Western Army, compared to the Army of the Potomac, which had a larger proportion of "townies" in its ranks.
Good and bad practice
The year 1863 saw the armies becoming more seasoned. As they did, the moments when engineering opportunities were lost became fewer, and the examples of good use of engineers, and of efficient performance by engineers, became more frequent. The Union saw a real maturing in its use of engineers. When Lee side-stepped west along the Rappahannock and moved north it was several days before Hooker realised that he faced only a screen. But as he moved north to counter Lee he ordered his engineers to construct pontoon bridges across the Potomac so that the Union army could cross into Maryland without delay and confront Lee. The bridges were in position, waiting for the army as it hurried north, indicating that the engineers had improved their ability to be in the right place, at the right time, with the right equipment since Fredericksburg.
A few months earlier Grant attempted to use the force of the Mississippi River to outflank the Vicksburg defences. The river described a U-turn in the Vicksburg area, so Grant ordered the digging of a canal across the neck of land, which would, had it been successful, have allowed river traffic to bypass Vicksburg. When the canal was dug and opened to the river, the Mississippi petulantly declined to flow through the canal to the extent required, and no navigable channel could be produced. Nonetheless, Grant's instinct was correct, for just a few years after the War the river did oblige, and tore through the neck of land, cutting the town of Vicksburg off from the river.
One serious error in the way engineer officers were used was the entrusting of the reconnaissance of the Confederate right flank in the early dawn hours of the Second Day of Gettysburg to a junior engineer. Lee had successfully carried out a similar feat as a young officer in the Mexican War, and this may have been a subconscious imitation. But every young engineer officer was not Lee. The hapless captain reported that the area that he scouted was unoccupied by the enemy, and he was then given to Longstreet to guide Longstreet's Corps onto the enemy flank. Whatever the actual state of occupancy of the area in question at the start of the day, the situation could not be guaranteed to remain unchanged throughout the day. Moreover, the engineer was then held responsible for the fact that part of the route crossed an open hilltop exposed to the view of the enemy. The debate then that led to the U-turn and counter-march by Longstreet's Corps appears to have been acrimonious and a serious case of awkwardness by Lee's senior and most experienced subordinate.
The final vignette, where the lack of a few engineers was a factor which seriously affected the outcome of the battle, was on the third day at Gettysburg. The most remembered moment of the battle was the charge, across a wide valley, of Pickett's Virginia Division. In the course of its advance the division crossed a major road which was bounded on both sides by a very substantial post and socket fence. Many of the fences in the battle area were of the zigzag snake rail fence variety, which were held together only by the weight of the fence posts above. However, this fence was stoutly constructed, and could not be pushed over. It could have been chopped down by pioneers with axes, had they been available, but they were not. Therefore the division, in the middle of an advance into the centre of the enemy position, and subject all the while to artillery fire from the front and the flanks, had to stop and climb the two parallel five foot high fences. This action disrupted the formation, slowed down the attack, and lengthened the time that the Virginians were exposed to the galling flanking fire. There are many accounts of troops deciding at this stage that they had had enough and of them electing to shelter in the lee of one or other of the fences. This certainly substantially reduced the number of soldiers who advanced beyond that point to push the charge home. To a modern observer the fence can be seen as having most of the desired effects of an anti-personnel minefield, namely of breaking up an attack formation, slowing down the attack, and lengthening the time that the attack is subject to defensive fire. It is also worth reflecting that, had Meade ordered a counterattack at the moment that the Confederates fell back, and then the counterattacking troops would have been similarly affected by the same fence when they advanced over the same ground.
SCORECARD North South Score N/S Field Defences Yes - Corinth (1862) Yes - Standard (1862) N:4 - S:8 Pontoon Bridges 1862, East Late 1863, East N:7- S:4 Railway Construction Yes, Standard No N:7 - S:0 Plank Roads Yes No N:4 - S:0 Mapping Average but standard Very good to very poor N:6 - S:5 Tools 1862, under Hooker Patchy N:7 - S:3 Total Score N:35 - S:20
In summing up, the scorecard above seeks to attribute a relative value to the performance of the two sides. It can be seen that only in the area of the use of field defences did the South perform better than the North. This can be attributed in part to the fact that the South stood on the defensive more than did the North. In almost all other areas, in the use of pontoon bridging, in the ability to rebuild railways, in the construction of corduroy or plank roads, and in providing hand tools, the North was organised more quickly and maintained the lead consistently. Only in the area of mapping does the South approach the performance of the North, but the North eventually developed an ability to reproduce sketch maps photographically in the field. The South got off to a good start in limited geographic areas, but at no stage was there a systematic effort to map all areas of interest in advance of the maps being required. Hence the muddle of the Confederate attempts to outflank the Union in the Seven days' Battles east of Richmond. There time after time the attacks arrived out of sequence, with one wing or the other getting lost in the maze of byroads, which were no more than a morning's ride from the State Capital.
The North tended throughout the War to rely too much on the innate skill of its citizen soldiers, rather than raise specialist engineer units. That said, the North engineers were better at inventing prefabricated, timesaving solutions. Particularly in the field of railways the North used modern engineering solutions, properly resourced, to sustain their advances.
However, to win the war the North had to advance, often over difficult terrain.The ability to do this would have been greatly enhanced if there had been enough combat engineers properly organised and equipped, to provide permanently assigned engineer support at the corps level.
The same criticism, that too much reliance was placed on the innate engineer skills of the soldiers, can be levelled at the South. The South was bound by its diplomatic stance to be on the strategic defensive, and they were much the quicker to realise and harness the power of the defence. However, as a whole the South did not invest many resources in combat engineering, and overall the standard of southern military engineering did not approach the professionalism of the Napoleonic Wars. Given the South's strategy of assuming the defensive and requiring the North to invade the South, it would have been perfectly possible for the southern authorities to have carried out a comprehensive survey of all the limited avenues of approach early in the War. This could have avoided many of the poorly executed attempts to cant' out flank marches early in the War, especially in the 1862 Seven Days Campaign, when southern manpower strength was at an all-time high. The lack of good mapping led to the debacle on Malvern Hill, and in hindsight it is easy to argue that this may well have cost the South the War.
(1) Pemberton was very short of cavalry at this time. He had had to detach his main cavalry force in January 1863 and in May 1863 there was a major Union cavalry raid, led by Colonel Grierson, which disrupted the railway east of Vicksburg. Such cavalry as Pemberton then possessed was chasing the raiders well east and south of Grant's chosen area of operations. Thus the Confederates had no way of keeping in contact with the Union force as it pushed inland.
(2) The Union suffered more than 4,000 casualties in the two unsuccessful assaults, whereas the Confederate defenders lost around 500.