Last week I looked at a study by a serving US Army officer, Maj. Thomas Erhart, about the need for longer range infantry weapons in Afghanistan. While looking at some of the supporting material I came across a fascinating study the Army conducted in 1960 (once classified secret) that led directly to the introduction of the smaller caliber M-16 rifle called “Operational Requirements for an Infantry Hand Weapon” (click for the complete study, which is in PDF format)
The study looks backward at American wars all the way back to the Civil War to determine average combat ranges, but it does more than that—the study authors try to determine why combat ranges fell out as they did. It includes interviews with veterans of WWII and Korea, and some historical data on earlier wars as well. Unfortunately the study is in poor shape, with portions of it being illegible, and I’d like to find a better copy.
What was the biggest single factor in determining engagement ranges? The ability to see your target. Once the rifle was introduced in the 1860s, you could hit what you could see, even if was quite a ways away. This was quite different from the Napoleonic period and earlier, where formations could maneuver on the battlefield in full view of each other with impunity. The conventional wisdom in Napoleon’s time was that a formation was safe from small arms fire at 250 yards and pretty much totally safe at 500 yards. This changed when the rifle was available, provided they could be seen.
The study looked at three types of terrain: Type A, such as found in Korea; Type B, close-in terrain such as that found near St. Lo, Normandy; and Type C, open rolling terrain such as that found near Gettysburg. Using a pretty sophisticated map analysis, they then tried to determine how far away you could actually see a target to engage it.
Here’s what they came up with. Percentage of hits is on the vertical axis, range 0-500 yards on the horizontal axis. The right curve (A) is the probability of a hit under ideal conditions, the left curve (D) is the probability corrected for actual battlefield conditions i.e. what you could actually see. It shows what I have long suspected—a sort of power law distribution. Most engagements and hits are at close ranges with the frequency dropping off steeply as the range increases, and almost none beyond 500 yards, even though the rifles would shoot almost three times that distance. This particular distribution has a very thin “tail.” In fact, the study concluded that almost all engagements took place at 300 yards or under, and the vast majority at 100 yards or less, which puts us almost back to Napoleonic ranges. Studies like this (the Germans did a similar one just before WWII) led to the development of the assault rifle with a less powerful cartridge and a decreased range, but with automatic fire rather than the bolt action or semiautomatic rifles of the WWII era. The study also concluded, based on Army marksmanship data at Ft. Benning, that only two men per squad could be counted on to become expert riflemen and use the full range of their weapons (which at the time was the .30 cal. M-1 Garand).
Conclusion? Terrain makes a lot of difference in weapons effectiveness. Until we have target-seeking ammunition you have to see what you can hit. There is of course a lot of difference in the battlefield of the Civil War, where everyone, at least until 1864, was still pretty much out in the open, and later wars where cover and concealment was the norm. But it provides a lot of food for thought.
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