How do historians know what happened to the Armenians in 1915?

The Armenian genocide is the name historians give to the destruction of Armenians in the Ottoman Empire during World War I. It was carried out under the ruling Committee of Union and Progress (CUP) and mostly consisted of death marches toward the Syrian desert, which killed around one million Armenians, along with the forced Islamization of others, primarily women and children.

How do historians know? The first source is the people at the time. The Ottoman Empire tried to prevent journalists and photographers from documenting the atrocities, but substantiated reports still appeared widely in Western newspapers. On 24 May 1915 Russia, Britain and France formally condemned the empire for "crimes against humanity and civilization".

The second source is paper. The events are extensively documented in the archives of Germany, Austria, the United States, Russia, France and the United Kingdom, and in the Ottoman archives themselves, even though incriminating documents were purged. There are thousands of eyewitness accounts from Western missionaries and Armenian survivors. Talat Pasha even kept his own statistics, which show a massive gap between those deported in 1915 and those surviving in 1917.

The third is the courts. After the war, the Ottoman Special Military Tribunal ruled that "the crime of mass murder" was organised and carried out by the top leaders of the CUP.

The word itself came from this history: Raphael Lemkin, who coined "genocide" in 1944, was drawn to the subject by the 1921 trial of the man who killed Talaat Pasha.

Almost all historians and scholars outside Turkey, and an increasing number of Turkish scholars, recognise the destruction of the Armenians as genocide. The Turkish government maintains that the deportation was a legitimate action against an existential threat, with no intention to exterminate the Armenian people, a position supported by the majority of Turkish citizens.