Allied troops at the ANZAC Cove in the Gallipoli peninsula, during World War I. Britain, France, Australia and New Zealand fought for nine months but could not defeat the Ottomans. Overall, a half-million were killed or wounded. Hulton Archive/Getty Images hide caption

itoggle caption Hulton Archive/Getty Images

Armenian refugees on the deck of the French cruiser that rescued them in 1915 during the massacre of the Armenian populations in the Ottoman Empire. The photo does not specify precisely where the refugees were from. However, residents of Vakifli, the last remaining Armenian village in Turkey, were rescued by a French warship that year. Photo 12/Photo12/UIG/Getty Images hide caption

itoggle caption Photo 12/Photo12/UIG/Getty Images

Prelates take pictures as Pope Francis celebrates an Armenian-Rite Mass to commemorate the 100th anniversary of the Armenian Genocide, in St. Peter's Basilica, at the Vatican Sunday. Gregorio Borgia/AP hide caption

itoggle caption Gregorio Borgia/AP

British and German soldiers fraternizing at Ploegsteert, Belgium, on Christmas Day 1914. World War I was raging at the time, but front-line troops initiated the truce, which they documented in photos and letters. Commanders on both sides were furious when they learned of it. Courtesy of Imperial War Museum hide caption

itoggle caption Courtesy of Imperial War Museum

Private Ernest Cable was buried in a cemetery in Wimereux, France. He died from dysentery in a hotel turned hospital in the northern French town. Courtesy of Genome Research Ltd hide caption

itoggle caption Courtesy of Genome Research Ltd

British servicemen and artist Paul Cummins (second from right) walk past his art installation "Blood Swept Lands and Seas of Red," made of ceramic poppies, during an Armistice Day ceremony at the Tower of London on Tuesday. Stefan Wermuth/Reuters/Landov hide caption

itoggle caption Stefan Wermuth/Reuters/Landov

Plaster casts taken from soldiers' mutilated faces (top row), new sculpted faces (bottom row), and final masks (on the table) sit in the studio of Anna Coleman Ladd in 1918. American Red Cross/Anna Coleman Ladd papers/Archives of American Art/Smithsonian Institution hide caption

itoggle caption American Red Cross/Anna Coleman Ladd papers/Archives of American Art/Smithsonian Institution

This installation at the Tower of London will ultimately feature 888,246 ceramic poppies, honoring the soldiers from Britain and the British colonies who died in World War I. Rich Preston/NPR hide caption

itoggle caption Rich Preston/NPR

Lourdes Garcia-Navarro with her husband, James Hider, and their dogs Nena (left) and Ursa. Tara Todras-Whitehill/Lourdes Garcia-Navarro hide caption

itoggle caption Tara Todras-Whitehill/Lourdes Garcia-Navarro

Charles Dillon Stengel had been known as Dutch — derived from the German Deutsch. Only after the U.S. went to war was Casey Stengel born. AP hide caption

itoggle caption AP

Nineteen-year-old Bosnian Serb Gavrilo Princip fired the shots that killed the heir to the Austro-Hungarian empire, Archduke Franz Ferdinand, and his wife, Sophie, during a visit to Sarajevo on June 28, 1914. Depending on whom you ask, he's either a hero or a terrorist. Historical Archives Sarajevo/AP hide caption

itoggle caption Historical Archives Sarajevo/AP