Trench warfare developed in response to improvements in weapons; The participants developed the trench system to provide defense against the enemy fires. Life in trenches had an appalling, monotonous schedule, intermittently interrupted by infrequent attacks. Trenches were usually flooded with mud and water, where dead soldiers lay with combatants. Many men killed in the trenches were buried almost where they fell, contributing to the spread of rats. Diseases such as dysentery, commonly acquired from contaminated water, was especially a problem during the first stages of the war.