Medical researcher Oswald Hope Robertson performed the first-ever blood transfusion using stored and refrigerated blood.
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Germany declared war on France and sent its first wave of troops to Belgium to start the attack.
Unofficial ceasefires sprang up across World War I's Western Front.
Battle of the Somme ends.
The Treaty of London was signed by Italy, Britain, France, and Russia.
Franz Ferdinand and his wife Sophie were assassinated, ultimately causing World War I.