Endurance, and danger
Zigzag - blast contained to a section; Periscopes - avoid many snipers
Covered landscape - 1000s of men; Front, support, reserve, at rest lines
Freezing cold, flooded = 24 hours; Quiet normal weather = 10 days
Sleep outside in case of surprise attacks, sleep on steps for movement
Terrible - Cold, muddy, rat-infested huts; Trench foot, other diseases common