Germany declared war on France and sent its first wave of troops to Belgium to start the attack.
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Unofficial ceasefires sprang up across World War I's Western Front.
During World War I, Japan officially declared war on Germany.
Medical researcher Oswald Hope Robertson performed the first-ever blood transfusion using stored and refrigerated blood.
The Treaty of London was signed by Italy, Britain, France, and Russia.
The Battle of Somme began.
