The military conflict characterized by trench warfare and chemical weapons is World War I, which lasted from 1914 to 1918. The war involved many of the world's great powers and was marked by a stalemate on the Western Front, where extensive trench systems were established. Soldiers faced horrific conditions, including mud, rats, and the ever-present threat of enemy fire. The war also saw the introduction of new technologies, including chemical weapons like chlorine and mustard gas, which caused devastating injuries and fatalities. The conflict fundamentally changed warfare and had lasting impacts on global politics and society.