Darkness: The trenches were typically shrouded in darkness to avoid being targeted by enemy fire. This made it difficult for soldiers to see, and movement was slow and dangerous.
Cold: Trenches were often located in muddy and damp areas, which made them cold and uncomfortable, especially during the winter months. Soldiers would often build small fires to try to stay warm, but these could also draw enemy fire.
Rats: Trenches were infested with rats, which were attracted to the food and waste that was ever present. The rats would spread disease and steal soldier's food, making life even more miserable.
Snipers: Snipers were a constant threat in the trenches. They would often hide in no man's land, the area between the opposing trenches, and target soldiers who exposed themselves.
Artillery: Artillery barrages were a common occurrence during the night. Soldiers had to be constantly alert for the sound of incoming shells, and take cover to avoid being hit.
Shell Shock: The constant stress of trench warfare, combined with the lack of sleep and proper nutrition, could lead to soldiers developing shell shock, a psychological condition similar to PTSD.
Despite the harsh conditions, soldiers had to be ever-vigilant. Enemy raids and patrols were a constant threat, and soldiers had to be prepared to defend their positions at any moment.