For Gettysburg itself, there was an unusual amount of night combat on the federal right flank. In general, the armies of the Civil War lacked any command and control capabilities to manage any complicated maneuvers at night. Unit cohesion would break down. Soldiers would get disoriented. There were a lot of friendly fire incidents. The CSA did try a night assault on the Federal right on the night of the second day's battle, but it was pitch black and they had trouble determining their own lines were, where the federal lines were, and any way of determining how to assault those position. The CSA soldiers would move forward towards the muzzle flashes, but even those became obscured in smoke.

The real threat to sleeping was night marches to new positions for either new defensive positions or for locations for an assault. But, keeping troops fresh was of a major concern. So, consider at the end of the first day at Gettysburg. Lee was sending orders to Ewell to assault the federal right "if practicable", but at the same time, Ewell's one division that had not seen heavy fighting that day (Johnson's Division) was just arriving on the battlefield around 7PM. Lee ordered them to bivuac instead of joining that potential assault. Lee wanted fresh troops for the following day. There were many, many examples of units starting their assault late the next day, or not at all, because they slept in over the course of the war. In some ways, it was far harder on the commanders and planners. They would often stay up pouring over maps, writing appropriate orders (or, inappropriate orders in the case of Burnside at Fredericksburg who had verbally given orders that were actually very good, but was so tired by the time he sent them out as written orders that they didn't match the verbal orders given earlier confusing the left wing commander who would be leading the main effort). Soldiers would also sleep as much as possible whenever they could during any lulls.

There were definite patterns. If tightly engaged, they would continue an assault, but if there were any breaks between the lines and a new assault would need to be planned and organized, they would generally not launch those until the following day. They would get the men into camp as soon as possible, then wake them up a few hours when it was still very dark to marching to the appropriate locations. Orders from the army commanders to the corps commanders, then down the line would almost always stipulate sleep times or breaks.

Another pattern that was remarkable was the shear percentage of battles where both sides knew which side would be taking offensive actions and which would be primarily defensive. It wasn't all the time and there were times, such as Stones River, where the opponents came up with the exact same battle strategy. But, one side would usually dig in on favorable ground and just wait for the assault. In general, night attacks were generally more used in raids where confusion and wanting to hide numbers were part of the plan.