"Troop density per mile" Topic

What was reckoned a sensible density per mile for formed troops in this era?

At Wagram the Austrians held a 14-mile front with 155,000 men, which is in ballpark terms 10,000 per mile. At Waterloo Wellington had 75,000 over 2.5 miles, which is three times higher at 30,000 men per mile. Borodino was about twice as wide as Waterloo with just under twice the forces, say 120,000 Russians, so 20 to 25,000 per mile.

Was there any standard doctrine on this whereby x width was considered too wide whereas y width was too dense and thus begging to be outflanked (or more than usually vulnerable to artillery fire)? 10 to 30,000 per mile is a big range.

I don't think there was any standard doctrine. Commanders deployed their troops as they thought best for the circumstances. Terrain and the likely movements of the enemy would be main factors.

Agreed – terrain is a huge factor, as the number of troops needed to cover 10 miles of flat plain is very different from that needed for 10 miles of mountain range

Agreed regarding terrain. The specifics of the batttlefield were the most important factor.

But one might also say that the British/Allied at Waterloo were rather sparse on the ground, a cause for concern at the time. On the other hand, the great density of troops at Wagram was also thought exceptional. So, for typical terrain, the 20,000-25,000 range per mile seems about right as an average.

When the opponent had the command and control and fast enough mobility, or roads to get around your flanks, the line of battle had to be widened. Amount of troops available being finite, density must be reduced.

18th Century armies being so much smaller in size to start with might mean a lesser density but the until the advent of the corps d'armmee, flank threats were much more local so forces were more likely to be kept closer to the center. lack of command control remains the biggest problem. The relatively independent mobility of Napoleonic corps being so much greater than 18th century makes any ideal density comparisons, apples vs oranges. They are very different ways of campaigning, even if the basic military principles regarding mass and economy of force haven't changed much from Cannae.

I am sure I've seen a figure of the ideal being 22,000 per statute mile quoted somewhere (maybe for lace wars).

If you allow 22 inches for a file you can get 2,880 files to a mile. (@ 28 inches = 2,262 fpm)

Two lines each three-ranks deep gives 17,280 (13,577)
Three lines each three-ranks deep gives 25,920 (20,365)
Two lines each four-ranks deep gives 23,040 (18,102)

Obviously these figures make no allowance for supernumaries nor for intervals between units and sub-units

At Wagram did the Austrians hold a solid single line, or was it clumps of troops? You may be comparing apples and oranges.