Operation Cyclone, described the first Stinger Mi-24 shootdowns in 1986 as one of the three crucial moments of his experience in the war, saying "we never really won a set-piece battle before September 26, and then we never lost one afterwards." He was given the first spent Stinger tube as a gift and kept it on his office wall. That launch tube is now on exhibit at the US Army Air Defense Artillery Museum, Fort Sill, OK. Other military analysts tend to be dismissive of the impact to the Stinger. According to Alan J. Kuperman, the Stingers did make an impact at first but within a few months flares, beacons, and exhaust baffles were installed to disorient the missiles, along with night operation and terrain-hugging tactics to prevent the rebels from getting a clear shot. By 1988, Kuperman states, the Mujahideen had all but stopped firing them. Another source (Jonathan Steele) states that Stingers forced Soviet helicopters and ground attack planes to bomb from higher altitudes with less accuracy, but did not bring down many more aircraft than Chinese heavy machine guns and other less sophisticated anti-aircraft weaponry. The last Stingers were supplied in 1988 after increasing reports of fighters selling them to Iran and thawing relations with Moscow. After the 1989 Soviet withdrawal from Afghanistan, the U.S. attempted to buy back the Stinger missiles, with a $55 million program launched in 1990 to buy back around 300 missiles (US$183,300 each). The U.S. government collected most of the Stingers it had delivered, but by 1996 around 600 were unaccounted for and some found their way into Croatia, Iran, Sri Lanka, Qatar, and North Korea. According to the CIA, already in August 1988 the U.S. had demanded from Qatar the return of Stinger missiles. Wilson later told CBS he "lived in terror" that a civilian airliner would be shot down by a Stinger, but he did not have misgivings about having provided Stingers to defeat the Soviets. The story of the Stingers in Afghanistan was popularly told in the media by Western sources primarily, notably in Charlie Wilson's War by George Crile, and Ghost Wars by Steve Coll. Angolan civil war The Reagan administration provided 310 Stingers to Jonas Savimbi's UNITA movement in Angola between 1986 and 1989. As in Afghanistan, efforts to recover missiles after the end of hostilities proved incomplete. The battery of a Stinger lasts for four or