What battle strategy used in ww1 allowed little ground to be gained

Options:

Allied war plan

Pershing plan

The French resistance

Trench warfare

The answer is trench warfare. This is a kind of land conflict using engaged fighting lines containing mainly of military channels, in which the troops are well sheltered from the opponent's small weapons fire and are considerably protected from weapon.

a type of combat in which opposing troops fight from trenches facing each other.