1915

January 19 - First German zeppelin air raid on England. 
February 4 - Any ship approaching Britain is considered a legitimate target as Germany declares a submarine blockade of England. 
February - Battle of Masuria. 
March - Battle of Neuve-Chapelle. 
March-December - Battles of Aubers Ridge and Festubert. 
April 22-May 5 - Second Battle of Ypres. First use of chemical weapons. 
April 23 - Allied assault on Gallipoli. 
May 7 - Lusitania sunk. 
May - Battle of Gorlice-Tarnow. 
August 30 - Responding to American demands, Germany stops sinking ships without warning. 
September 5 - Tsar Nicholas commander of Russian armies. 
September-October - Battle of Artois & Champagne. 
September-October - Battle of Loos. 
December 7 - David Lloyd George becomes Prime Minister of Britain. 
December 28 - Allied withdrawal from Gallipoli. 
December-April, 1916 - Siege of Kut.