Turkish involvement in the Syrian civil war
Turkish involvement in the Syrian civil war began diplomatically and later escalated militarily. After a decade of relatively friendly relations with Syria from 2000 to 2010, Turkey condemned Syrian president Bashar al-Assad over the violent crackdown on protests in 2011 and, from the beginning of the war, Turkey trained defectors of the Syrian Army in its territory under the supervision of the Turkish National Intelligence Organization (MİT), among whom emerged the Free Syrian Army (FSA) in July 2011.
Source: Wikipedia — Turkish involvement in the Syrian civil war (CC BY-SA 4.0)