Very well put Ron regading entrenchments.
Entrenching and fortifications underwent an incredible evolution during the war, mainly from the bottom up. Both ANV and AofT (not AoftheT) discovered to offset the numbers in men and superior artillery of the US, they had to be innovative in the digging of entrenchments. In 61, 62 and even as late as 63, entrenchments were centralized and overseen, sometimes planned in advance. Also, they confirmed to engineering principles, not reality. Though they still offered far more protection than being on line in the open, they had issues with artillery and enflade fire.
Another thing the CS would do was to entice the US to attack their lines. This is not talked about much by authors, don't know why, but it explains why several attacks were made such as Sherman's assault at Kennesaw. This was not due to the Union Commanders not knowing the true strength of the positions, they did but they felt many times they had found gaps and wanted to exploit them. It was just hard to reconnoiter, if they could see them at all, the Confederate lines. The Confederates realized that if they were going to get the US to attack their strength, as well as avoid Federal artillery fires, they had to blend the lines into the earth, not camoflage as we know it, but just use the terrain to help protect and keep the US from seeing what was going on. They would cut trees down behind and not forward of the line, and just to abatis as well. When they did not do this, as at the incredible Chattahoochee line, where Sherman could see the lines several miles away and observed that it was the strongest line he had ever seen, the US would not attack (some of this incredible line remains on a park on the southern end of the line just across from the smaller Atlanta airport off the beltway as it crosses south of the river from the
northhttp://ngeorgia.com/ang/Chattahoochee_River_Line-).
I have walked almost every position in the east and west in 64 and see the same trend. Very rarely to see the picture perfect Field Manual position with big open fields of fire.
By 64, entrenchments became part of every battle to equal as Ron pointed earlier, to WWI.
First, the Kennesaw line would have had abatis at it everywhere. Johnson had this planned for weeks, each position was fell back too, was marked if not partially prepared by slave labor. When a brigade stopped, and had any time to entrench, it would lay out a formidable line in a few hours. When it was told to lay out a line where engineers would mark with sticks and cloth before hand (as Joe Johnson did during Atlanta so his men had a place to fall in on in the dark), the men and officers would arrive and confirm it to the contour of the terrain, if not under fire. Big difference when not having the stress of no fire and being fired at, still the men could dig, especially under fire, but did not have time to confirm the line to the terrain or create abatis, as well as to develop beyond just having the main line.
If they had time, meaning a day or one night, by 64, the brigade would task a regiment as skirmishers, and the remaining units would dig their own lines with 1/3 cutting abatis, 1/3 cutting and laying trees and the remaining 1/3 digging. Within 4-6 hours, sometimes even faster, there would be a line confirming to hidden terrain (almost similiar to what we know as reverse slope defenses), abatis woud be up (and constantly improved on), there would be traverses, at few meters (to offset enflide fire as well as to seal off penetrations. As the lines would improve, supplementary positions would be dug, ammo dug in, and rifle pits for pickets/skirmishers would also be added, as well as bomb proofs as they stayed longer. (several times when I was reenacting with Thomas Mudsills or Sherman's Bummers, about twice year, we would be at events where we got to dig, and find out that we could have pretty substantial positions working together in a few hours, and more than half the participants were not any shape like the real guys nor under the stress to survive).
Also, artillery dug their own positions. I cannot understand why this cannot be an addition to the games. You would not have just the infantry dig in, with the guns in the open. By 64 artillerymen became as proficient as the infantry in digging their gun pits quickly and efficiently! Anyway, you think the infantry are going to dig in the artillerymen, especially since the artillerymen get to carry more gear then the infantry does? NO way, though non horse artilleryman walked as did the infantry with field packs, they were still able to carry shovels and picks. How many times have we played where we get all the infantry dug in and the guns are out in the open (behind the infantry (another subject of deployment). By 64, the CS would blend their guns among their lines, where as the Federals would see seperate battery positions slighty behind and higher than the infantry line. For good examples of these differences, walk the Federal and CS positions at the Battle of Wilderness and Spotslvania, as well as at Cold Harbor, here a lot of Federal works remain, and there is still a difference.
The best examples of trenches I have seen throughout the US Civil War parks and sites is at North Anna River off I-95 west of King's Dominion off Route 1 in Virginia. It is a county park with several hundred acres, and excellent walking trails with small signs and maps. As you go through, you will see that the entrenchments are still formidable, but also odd. Well, the traverses and supporting works constantly change every few meters. Well it was left to each regiment how they dug them, and usually traverses were placed between companies, sometimes platoons. You will also see positions for command posts, ammo caches and great artillery positions. There remains several miles of entrenchments on and off the park (Civil War Trust is continually negotiating with a rock quarry company to buy more). Unfotunately few Fedeal trenches remain except on the far eastern side of the battlefield near the original Telegraph Road bridge on the south side on private land.
Another thing I would add to the games, but not knowing software development (I am only a military historain), and having a great discussion with Ron while we played the Mother of all Battles from Shiloh, would have entrenchments progressively get better as they were occupied longer. There should be also an option to build abatis, which did not take the men long to chop down and meld trees tops toward the enemy, then chop and sharpen branches.
There are currently a lot of great books on the evolution of trenches in the Civil War, including a series in the east at the Overland campaign and Petersburg: In the Trenches at Petersburg: Field Fortifications and Confederate Defeat, which has entire series with great photos in it.
Take care, Don