All right a quick pop test, as an individual soldier in combat in battle which time period was more dangerous to you:
a) Classical Roman Empire
b) American Civil War
c) World War 1
d) World War 2
But first: A Chart.
And the answer is: a) Roman Empire.
By Trevor Nevitt Dupuy
Dupuy wrote a good deal about casualties in battle. He showed that except for two little jumps up (Napoleonic Period, and American Civil War Period) losses dropped fairly consistently through time as technology advanced.
Yes the armies were (generally) smaller, yes the later weapons are more destructive, and yes more people overall were killed on the latter battlefields. But a combat soldier in battle during the time of the Roman Republic: particularly if you were on the losing side, had a much higher chance of being killed. A soldier on the losing side of a modern battle has less of a chance of being killed than a soldier of the winning side in any time before 1900.
The primary reason that casualties dropped, is that as weapons got deadlier, armies spread out, started hiding, and started digging in. In fact clearly one of the blip-up periods (American Civil War) was a time period when there were advances in weaponry, but the troops did not spread out or take cover until latter in the hostilities. As further illustration, although the trenches of World War 1 are famous for the futile assaults, the early period of open battle in 1914 was the deadliest phase of the war. Only after the armies had blasted themselves to pieces, culminating in the Battle of the Marne, did the trench warfare start.So distance, along with dispersion, concealment, and cover count for a lot.
To continue the discussion at a more tactical level , Tests by the U.S. Army found that it was often difficult to even see your enemy. Based on data from both WW2 and Korea, the success rate at 100 yards was only 80%, at 200 yards only 40% At 300 yards the was only spotted 20% of the time. By the time you get to 400 yards a very slim 5% chance of spotting your target.
Norman Hitchman, et al. Operational Requirements for an Infantry Hand Weapon, Operations Research Office, Johns Hopkins University, Chevy Chase, MD, 1952.
Gabe Suarez has done some additional research with unloaded rifles in open country with variety of moving, running, standing still, and hiding targets (people) His observation was:
Unless you are already monitoring an area for movement, you will probably not see a man further than about 300 yards. Thus your 200/600 yard standards make good sense. Truly we could cut the distance to 500 yards and still be real world relevant. Gabriel Suarez - Warrior Talk News - The Guerilla Sniper Revisited.
Not that this is in open country. If I go to the closest cross road near my house (a subsidiary feeder street), my longest sight line is about 85 yards. With a little work I can find a slightly elevated location where I can see about 150 yards down this road. Even when the Google Satellite view shows a clear LOS, folds and elevation changes give a lot of cover for someone attempting an approach.