Trench warfare is fighting between two opposite sides with soldiers dug into ditches on either side with "No Man's Land" inbetween. It usually consists of soldiers, sometimes tanks, and usually artillery. One side would send wave after wave into No Man's Land untill they gave up or the opposing Trench was overrun. Trench warfare was first used in World War 1 and continued as a style of fighting for years to come.
Charles V: Men, You will be sent into Trench Warfare in France against the Germans.
Kaiser Wilhelm: We will also use Trench Warfare!