True. If you are in a trench, you are literally sitting in a hole in the dirt for hours on end; sometimes keeping watch, sometimes in the heat of battle. If you get injured, there are tons of diseases in the dirt and from humans just sitting in that hole for large amounts of time, usually without showering for days or weeks (depending on where you are and the resources available). Injury, you could get shot in the shoulder while firing, or someone could throw an active grenade into the trench and, well, it wouldn't end well. Mud-- you're sitting in a hole, in the dirt. If it rains, you are now sitting in a wet hole in the dirt, and dedication to your country--or flying bullets--is keeping you there.
