By Stijn Mitzer and Joost Oliemans
The Su-24 represents the most modern and main strike element of the Syrian Arab Air Force (SyAAF). They have taken an active part in the Syrian civil war since November 2012. While most of the SyAAF attack aircraft are already worn out and struggling to cope with the high demands, the Su-24s just received a full factory overhaul in Russia, ensuring they can maintain a high operational tempo.
Syria received a total of twenty Su-24s since 1990. Twenty Su-24MKs were ordered from the Soviet Union in 1988 and delivered in 1990. The fleet equips 819 squadron based at T4 in the middle of Syria with a few planes being detached to Seen in the South. The MK version Syria received was a downgraded variant of the Su-24M, the M being built for the Soviet Union and the MK for export customers like Algeria, Iraq, Iran, Libya and Syria.
Although little known to the public, the whole Syrian Su-24MK fleet was upgraded to M2 level in the past years. All twenty Su-24MKs were upgraded to MK2. The MK2 upgrade brings the Su-24s on the same standard as the Russian Su-24M2s. The upgrade provides for improved targeting, navigation and fire control systems by replacing the plane's old control systems. The plane is also being made compatible with newer versions of the KAB-500/1500 and for Kh-31As, Kh-31Ps, Kh-59s and R-73s.
The contract was signed in 2009 and work started in 2010, with most of the upgrades completed in 2013. More than half of the twenty-one upgraded Su-24s made it back to Syria without any problems, but up to ten of them weren't so lucky and were still stuck at Rzhev last autumn.
|Five Syrian Su-24s at Rzhev on the 30th of July 2012|
However, given the importance of Su-24M2s to SyAAF, Assad regime must have done its utmost to recover its most advanced attack aircraft sitting idly in Russia. According to a source that wants to remain anonymous, the SyAAF was already working to have them delivered a year ago. This of course being a strict violation of the arms embargo.
The example of the well-known Mi-25 deal shows that after the Russian ship carrying overhauled helicopters to Syria was forced to turn back because of the imposed embargo, those Mi-25s were nevertheless delivered to Syria in a covert deal. 
The lack of publicity on the Su-24M2 deal should have only made the delivery easier, so we may safely assume that the aircraft most likely have already made it back to Syria. New satellite photos of Rzhev can make that clear when they come up on Google Earth or other services.
On the 28th of November 2012, a SyAAF Su-24M2 was shot down above Daret Izzah in the Aleppo Governorate, making it the first loss of a Su-24 in the conflict/
The SyAAF also used her Su-24s to test the British Air Defence around Cyprus on the 2nd of September and the Turkish Air Defence on the 5th of October. A military intervention would likely have been carried out from Akrotiri, Cyprus. This would be a logical target for the SyAAF, hence the testing of the British reaction time.
Syria's recently upgraded Su-24s (2)