Registration of US men aged between 21 and 31 began for troops for WWI.
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After nearly four and a half years of cataclysmic conflict, World War I ended.
The Battle of Somme began.
Medical researcher Oswald Hope Robertson performed the first-ever blood transfusion using stored and refrigerated blood.
Unofficial ceasefires sprang up across World War I's Western Front.
Tanks were used for the first time in battle, at the Battle of the Somme, during World War I.
