The Armenian Genocide began in April 1915, when the Ottoman government in Istanbul rounded up hundreds of Armenian intellectuals and deported them to Ankara. Soon afterward, an order was issued to relocate ethnic Armenians away from Turkish-inhabited areas through death marches. This relocation program was accelerated after the Siege of Van, during which Armenian defenders attempted to resist the invading Ottoman armies. Those who managed to survive the marches were sent to extermination camps located along the present-day borders of Iraq and Syria. Starting in 1919, the perpetrators who had not already fled Turkey were court-martialed, but the Pashas who were the heads of the Committee of Union and Progress (the political party that carried out the genocide) had already fled the country.
To this day, the Turkish government continues to deny that the Armenian Genocide ever took place, and resents the Armenian government for bringing it up regularly at international forums, making it a major bone of contention in diplomatic relations between the two countries. To this day, referring to the Armenian Genocide as such remains illegal in Turkey.