January 1915 - Dardanelles campaign beings, request from Russia that was intended to cut off Turkish forces.

February 4, 1915 - Germany declares blockade of Britain.

March 1915 - Battle of Gallipoli, Dardanelles expedition to gain Constantinople. Mission extended into October but failed multiple times.

April 1915 - German attacks Ypres with no strategic purpose other than to try out a new weapon - chlorine poison gas.

April 26, 1915 - Italy signs the secret Treaty of London which promises Italy regions south of the Alps, South Tyrol, areas of Slovenia, Dalmatic and a share of Turkish Anatolia.

May 7, 1915 - U-Boat sinks the Lusitania, creates a crisis between Germany and the U.S.

May 23, 1915 - Italy enters the war.

October 1915 - Bulgaria enters the war on the side of the central powers.

November 1915 - Austria, Germany and Bulgaria form a three-way attack on Serbia. Serbia is invaded, falls and is occupied.

November 1915 - Allies meet in Chantilly to discuss plans for victory in 1916.

December 19, 1915 - Sir Douglas Haig replaces Sir John French as British Commander.

End of 1915 - German record on the eastern front is one of unbroken success.