Direct proof of use
Syrian Arab Air Force MiG-23s were documented in combat operations during the Syrian Civil War. A Washington Institute assessment of Syrian Air Force operations listed MiG-23s among the fixed-wing combat aircraft principally used for strike missions in the war, alongside L-39s, MiG-21s, MiG-29s, Su-22s, and Su-24s.
The clearest dated incident occurred on 23 March 2014 near the Turkish-Syrian border. Turkey said two Syrian regime fighter aircraft approached its border, one turned back after warnings, and the other violated Turkish airspace before Turkish aircraft engaged it. Reporting by BBC, Al Jazeera, Daily Sabah, Time, and Air & Space Forces Magazine identified the aircraft or Syrian MiGs involved as MiG-23s or MiG fighters and placed the crash near Kasab/Kesab in Syrian territory.
Sources: Syrian Air Force Operations, Turkey MFA Syrian Warplane Press Release, BBC Turkey Downs Syria Military Jet, Al Jazeera Turkey Shoots Down Syrian Fighter Jet, Daily Sabah Turkish Armed Forces Alert, Time Turkish Military Shoots Down Syrian Jet, Air & Space Forces Turkish Fighters Shoot Down Syrian MiG-23
Narrative
In the Syrian Civil War, the MiG-23 appeared as an aging but still active government-side fighter-bomber rather than as a modern air-superiority platform. The Syrian Air Force used fixed-wing combat aircraft to support regime ground operations, attack rebel military targets, strike movement and logistics, and conduct close air-support missions. MiG-23s were part of that fixed-wing strike inventory.
The 23 March 2014 incident shows how MiG-23 operations intersected with the war's border fighting. Al Jazeera reported that the Syrian Observatory for Human Rights said the aircraft had been striking areas in Latakia as rebels tried to control a border post. BBC reporting similarly quoted a Syrian military source saying the jet was attacking rebels, while Turkish statements said repeated warnings preceded the engagement after an airspace violation. The aircraft fell on the Syrian side of the border, and reports said the pilot ejected.
Sources: Syrian Air Force Operations, BBC Turkey Downs Syria Military Jet, Al Jazeera Turkey Shoots Down Syrian Fighter Jet, Turkey MFA Syrian Warplane Press Release, Time Turkish Military Shoots Down Syrian Jet