In late 2015 Russia told Syria it would upgrade its air force. This included some additional warplanes, like ten Su-24M2 light bombers. By mid-2016 the first two were delivered. Syria had 24 of the older Su-24s when the civil war began in 2011 and most of those have since crashed or been grounded because of age related problems. The M2 models are the latest Su-24 upgrades and were performed on recently (late 1980s or early 1990s) built Su-24s that didn’t get much use because of the Russian Air Force was broke during most of that period. The M2 improvements include modern electronics (all digital, flat panel screens, GPS and so on) and improved engine reliability. The aircraft were also equipped to deliver all the latest smart bombs. The M2 upgrade enables Russia to get the most out of the few flyable Su-24s it still has in service. Syria still has pilots and ground crews with experience flying and maintaining the Su-24. The newly arrived Su-24M2 were soon seen in action.
The Russian Air Force is currently in the midst of replacing its 300 active Su-24M2s with a hundred or so of the new Su-34s. During the Cold War the Su-24 was the Russian answer to the American F-111 and European Tornado fighter-bombers. Introduced in the mid-1970s, it was a 43 ton swing-wing design with a crew of two and a short range (only about 600 kilometers). The original Su-24 carried eight tons of bombs and had good fire control and electronics for the time. Some 1,400 were built before production was halted in 1993. Since then most Su-24s have been retired because of old age and lack of upgrade options. Since 2000, about twenty Su-24s have been lost due to accidents. Many more have been retired because of this tendency to become very dangerous to operate as they age. This is one of the reasons Russia is hustling to replace the Su-24s with Su-34s. Meanwhile there are dozens of recently upgraded Su-24M2s.
In 2008, Russia began building the first Su-34 fighter-bombers. The 45 ton Su-34 is yet another variant of the thirty-three ton Su-27 and is very similar to the thirty-six ton U.S. F-15E (a two seat fighter bomber version of the 31 ton F-15C). The Su-34 has a full set of defensive and offensive sensors (radars, targeting cameras, laser designators) and electronic warfare gear, it also can carry eight tons of missiles and smart bombs. The Su-34 has been in the works since the 1980s and didn’t enter service until 2014.