There's a lot of theoretical stuff written about "Revolutions in Military Affairs". Here's some down to earth changes that came about in the Great War.
It remains to mention two allies of [the WWI] infantrymen that virtually revolutionized their combat methods. The first was the motor truck, which gave foot soldiers greater mobility than they ever before had.
The second was a miscellany of signal equipment. This helped the infantry to operate with some degree of coordination on huge battlefields where arm signals could no longer be seen and noise drowned out the human voice. It aided in making foot troops an effective instrument of the will of the commander and served to rectify, at least a little, the disorganization that resulted from the necessity for soldiers to disperse widely in order to survive.
|Signal Corps SCR-54A radio set, a crystal radio receiver
used by the US Signal Corps during World War I
Sources: Infantry, Office of the Chief of Military History, U.S. Army; photos from Steve Miller and Wikipedia