By 1915, the war had settled into a deadly stalemate on the Western Front. Soldiers faced mud, barbed wire, shellfire, disease, and exhaustion as trench warfare became the defining image of the conflict.

At the same time, the war widened. Fighting expanded across new fronts, including Gallipoli, the Alps, and the Eastern Front. Italy entered the war in 1915, and the Ottoman Empire remained a major force in the wider conflict.

This was also a year of military experimentation. Poison gas appeared on the battlefield, but despite new methods and enormous losses, no side achieved a decisive breakthrough.

Key themes for 1915:

• Trench warfare becomes the defining reality of the conflict
• Gallipoli opens a major new campaign
• Italy enters the war on the Allied side
• Fighting expands on the Eastern and Balkan fronts
• Poison gas appears as a new weapon
• No side achieves a decisive breakthrough