February 4, 1915. In response to the British blockade of Germany, the Germans announce that they will begin to attack any vessels, neutral or not, sailing in the waters of the British Isles. Although the British navy controlled the ocean’s surface and the british were already searching for and confiscating any goods bound for Germany that could possibly be helpful in the war effort, German U-boats (submarines) and their policy of unrestricted submarine warfare would prove to be a valuable weapon for Germany.

April 22, 1915. The Germans introduce the use of poisoned gas as a weapon in the war in the Battle of Ypres on the Western Front. The first poisoned gas is not very effective, but the Germans promise that “more effective substances can be expected.” Anti-chlorine gas masks are issued to British troops.

April 30, 1915. Allied forces, mostly British, Australians, New Zealanders and French, land on the Gallipoli Peninsula in Turkey in an attempt to force an entrance through to the Black Sea and supply weapons and goods to Russia through her ports there.

May, 1915. In spite of a German warning that “a state of war exists between Germany and her allies and Great Britain and her allies”, the Lusitania leaves New York bound for Liverpool, England. The Germans advertise in the New York newspapers, “Vessels flying the flag of Great Britain, or any of her allies, are liable to destruction . . . travelers sailing in the war zone . . . do so at their own risk.” Passengers filled the ship anyway, and on May 7, just off the coast of Ireland, a German U-boat fired on the Lusitania and caused it to sink. 1,198 people died, and 128 of them were Americans. Many Americans advocate war against Germany, but President Woodrow Wilson continues to counsel and pursue peaceful negotiations with the Germans.

May 23, 1915. Italy leaves the Triple Alliance (Central Powers) and goes to war against Austria-Hungary, joining the side of Britain, France, Russia, and Serbia.

June, 1915. Armenians, a Christian minority in a mostly Muslim Turkey, are seen as traitors and potential rebels. So the Turkish government begins a program of deportation and secret genocide for the Armenians. The Road from Home by David Kherdian tells the story of the author’s mother, Veron Dumehjian, who was a 15 year old survivor of the Armenian holocaust. It’s an excellent book.

July 29, 1915. 400 U.S. Marines land in Port-au-Prince, Haiti, to protect American lives and property as revolution and civil war rage throughout the small island country in the Caribbean.

September, 1915. Bulgaria enters the war on the side of Austria and Germany and moves its troops eastward toward Serbia.

November 14, 1915. Tomas Masaryk, a professor of philosophy exiled by the Austrians, calls for a free Czechoslavakia —combining the two parts of the Austro-Hungarian Empire into one free country.

December 20, 1915. After eight months of fighting, Allied forces retreat from Gallipoli Peninsula leaving it in Turkish hands. Newspapers call the retreat the biggest setback of the war so far for the Allies.

December, 1915. German physicist Albert Einstein publishes his new Special Theory of Relativity.