In 1914, Europe moved from diplomatic crisis to full-scale war. The assassination of Archduke Franz Ferdinand at Sarajevo triggered the July Crisis, a chain of decisions, ultimatums, and mobilizations that pulled the great powers into conflict.

Germany backed Austria-Hungary, Russia supported Serbia, and France and Britain were drawn in as alliances hardened. The German invasion of Belgium brought Britain into the war, while the opening campaigns in the west led to the Battle of the Marne.

By the end of 1914, hopes for a short war had collapsed. Trenches began to stretch across the Western Front, and the conflict was already becoming a long and brutal struggle.

Key themes for 1914:

• Sarajevo and the July Crisis
• Declarations of war
• The Schlieffen Plan
• The Battle of the Marne
• The beginning of trench warfare