Hasan Tahsin (born Osman Nevres) (1888 Selanik - May 15, 1919 İzmir) was a Turkish journalist and is a national hero in Turkey. A member of the Ottoman Secret Service (Teşkilat-ı Mahsusa), he unsuccessfully tried to assassinate the Buxton Brothers in Romania during World War I.
He was the first to open fire on the Greek soldiers that landed in İzmir on May 15, 1919, in the opening act of the Greek occupation of more than three years that extended over a large part of western Anatolia, as well as of the Greco-Turkish War (1919-1922). As such, his name came to symbolize the date of 15 May 1919 in Turkey, and is associated with the events that occurred in İzmir on that day. His opening fire on Greek troops led to intercommunal rioting which killed over 300 people.

Source: Trekearth