Martyrs' Day is an official remembrance day and public holiday in Syria and Lebanon.
It is observed annually on May 6 to commemorate the Lebanese and Syrian nationalists executed in Beirut and Damascus on this day in 1916.
The territory of present-day Lebanon and Syria had been ruled over by the Ottoman Empire from 1516 to 1918.
It was part of the so-called Greater Syria.
Following the Young Turk revolution of 1908, Arab nationalism in Greater Syria began to gain momentum.
On May 6, 1916, 21 Arab nationalists were simultaneously publicly executed in Beirut and Damascus for alleged anti-Turkish activities by Jamal Pasha's order.
This eventually led to the Arab revolt.
The date of execution is now commemorated as Martyr's Day in Lebanon and Syria.
Sites of execution have been renamed Martyrs' Square in both cities.