On April 24, 1915 hundreds Armenian Intellectuals: poets, musicians, publicists, editors, lawyers, doctors, deputies, were arrested in Constantinople under warrants issued by the Turkish authorities. They were all sent into exile and were horrifically slaughtered. The annihilation of the Armenian Intellectuals was the part of a systematic, fiendish plan to exterminate the Armenian people in their homeland. It was the first state-planned Genocide of the 20th century.
The date was chosen by Lebanese Armenians to commemorate the 50th anniversary of the Genocide in 1965. The same day witnessed illegal demonstrations staged by Armenians in Yerevan the capital of Soviet Armenia. The Armenian protests got out of control and calm was restored with difficulty.
On 9 April 1975, the US House of Representatives passed Joint Resolution 148 designating 24 April as a National Day of Remembrance of Man’s Inhumanity to Man. The Resolution commemorated the victims of genocide, especially those of Armenian ancestry who succumbed to the genocide perpetrated in 1915, The resolution however failed to pass in the U.S. Senate Judiciary Committee due to President Gerald R. Ford’s strong opposition to what he saw as a threat to the country's strategic alliance with Turkey.
Popularity of the day rose in diaspora as a result of anti-Turkish operations by Armenian groups such as the ASALA, and attendance of Genocide Day demonstrations rose in France from several hundreds to over 10,000 in 1981.
Soviet Armenia formally adopted 24 April as a public day of commemoration in 1988. In 1997 the California State Assembly declared 24 April as a Day of Remembrance for the Armenian Genocide of 1915–1923, and for the victims of the Sumgait Pogroms of 1988 and Baku Riots of 1990.
The day is also chosen by Assyrian/Syriacs to commemorate the Assyrian Genocide especially in diaspora.