While forces from the Ministry of Interior are often involved in locating spies and saboteurs, the Spetsnaz units of the Ministry of Defense have been more directly involved in the war. Perhaps the most well known are the Spetsnaz units responsible for defending Donetsk International Airport. The Airport was raided on April 18, but maintained operations until May 25, 2014 after which it faced nearly daily attacks. The 3rd Separate Spetsnaz Regiment have earned the nickname "Cyborgs" and has been involved in the Second Battle of Donetsk Airport. Rebels have on multiple occasions stated that they have captured the airport, however the flag of Ukraine has been flying over the dispatch tower, suggesting the airport was actually not captured. The airport's garrison has been able to withstand attacks by Russian T-72 tanks, Grad and Uragan rocket artillery, as well as 2S4 Tyulpan heavy mortars without any air support. By September, Russian Spetsnaz forces began to actively aid the rebels in assaulting the airport, however, they only managed to advance 500 meters closer to the complex by the end of the month.