The conflict characterized by trench warfare and the use of chemical weapons was World War I, which lasted from 1914 to 1918. One of the most notable features of this war was the extensive use of trench systems, where soldiers battled under harsh conditions, leading to significant loss of life and psychological trauma. The introduction of chemical weapons, such as mustard gas, marked a horrifying evolution in warfare tactics, causing severe injuries and long-term health issues for those exposed. The devastating casualties and horrors of trench warfare during WWI fundamentally changed military strategies and had profound social and political ramifications worldwide.