24 April 1915,
The anti-Armenian genocide begins in the Ottoman Empire. I. It all started with the night execution of 600 Armenians in Istanbul during the World War. In a few months, two-thirds of the Armenian empire disappeared. In eight years, until 1923, about 1.5 million Armenians died and about one million were deported in the Death Marches, through the Syrian deserts. Turkey still denies genocide.
Source:
Vicken Cheteria, The Armenian Genocide and Their Further Lives (Le Monde Diplomatique, April 2015)