On Vladimir’s comment: one element that substantially deepened Australian gains in the August 8 1918 battle near the Somme was a battalion of 8 armoured cars. Even limited to road travel, the armoured cars were able to push into what had been German rear areas and disrupt communications, supplies, and morale.

When the cavalryman cannot gallop under fire, the infantryman cannot march under it. Battles will consist of exchanges of rifle shots by concealed men, at long range. The battle will end only when the ammunition is exhausted.

I suppose this was meant as a reductio ad absurdum, but in retrospect it looks like a correct prediction about what happened in WW1.

Once armies obtained something akin to cavalry capable of galloping under heavy fire (i.e. tanks), war indeed became a dynamic game of maneuver much like what Du Picq imagined here. But it certainly seems like he was carried away by wishful thinking about the prospects of cavalry (and chivalric?) warfare in the industrial era.

The Western fronts were simply too dense with men (said density enabled by the density of the logistics network of France and Belgium) to allow cavalry units the freedom to maneuver. Every attack is a frontal attack if there are no flanks.