This photograph shows two members of a trench mortar crew of the 3rd Canadian Division. These men worked with a weapon called a mortar. Mortars shoot explosive shells out of a tube at a steep elevation angle to hit enemies at shorter ranges. Mortars were very beneficial in the trenches, since they allowed soldiers to attack enemies (even enemies in trenches) without the mortar crewmen leaving the cover their own trenches.
Mortars and artillery pieces, such as howitzers and field guns, were used extensively in World War I. Since these weapons are often fired from great distances, soldiers on both sides were capable of hitting enemy soldiers both inside and outside of trenches with a well-aimed shot.