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Britain and France declare war on the Ottoman Empire.
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World War I begins when Austria-Hungary declares war on Serbia.
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First Battle of the Marne begins. The Germans had advanced to within 30 miles of Paris, but over the next two days, the French are reinforced by 6,000 infantrymen who are transported to the front by hundreds of taxis.
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Archduke Franz Ferdinand of Austria and his wife, Sophie, are assassinated by a Bosnian Serb nationalist in Sarajevo who was part of the black hand group. -
Germany declares war on Russia, France, and Belgium. Britain declares war on Germany. Austria declares war on Russia. Montenegro declares war on Austria. France declares war on Austria. Britain declares war on Austria. Montenegro declares war on Germany. Japan declares war on Germany. Austria declares war on Belgium. -
The Second Battle of Ypres begins. The German army initiates the modern era of chemical warfare by launching a chlorine attack on Allied trenches. 5,000 French and Algerian troops are killed. -
The Battle of Verdun begins. Over the next 10 months, the French and German armies at Verdun, France, suffer over 700,000 casualties, including some 300,000 killed. By the battle’s conclusion, entire French villages had been wiped from the map.
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The First Battle of the Somme begins. The British offensive is intended to draw German attention from Verdun, and in that regard only could it be considered a success. The nearly 20,000 killed in action on July 1 marks the single bloodiest day in the history of the British army. Four and a half months later, the combined casualties of both sides topped 1,000,000. -
The British and German fleets meet 60 miles off the coast of Jutland, Denmark, in the war’s only major encounter between the world’s two largest sea powers. A naval arms race between Britain and Germany had been one of the causes of World War I. -
The United States declares war on Germany.
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France marks the first large-scale use of tanks in combat. Attacking with complete surprise, the British tanks ripped through German defenses in depth and took some 7,500 prisoners. Bad weather intervened, however, and reinforcements were not available to take advantage of the situation. Within two weeks, the British had been driven back almost to their original positions. -
After months of delays, the Soviet government concludes a separate peace with the Central Powers when it accepts the Treaty of Brest-Litovsk. Russia surrenders its claim to Ukraine, to its Polish and Baltic territories, and to Finland. -
German offensives that year had been defeated with heavy casualties, and in late summer and fall, the British, French and U.S. forces had pushed them steadily back. With the United States able to send more and more fresh troops into combat, the Germans were outmatched. The ability of Germany to continue the war seemed doubtful at best. The armistice between Germany and the Allies was the first step to ending World War I.