In 1973, it was reported that a force of 40 Mirage IVs would continue to perform as a part of France's nuclear deterrent until the 1980s, and that steady improvements were to be undertaken. In 1975, all Mirage IVs were progressively painted in a new green/grey camouflage scheme. In 1979, in response to the decreasing effectiveness of free-fall bombs used by both its strategic and tactical nuclear forces, development of the ASMP stand-off missile was initiated; the ASMP would possess a range of up to 400 km (250 mi) and was alternative armed with either a single 150 or 300 kiloton nuclear warhead. Various test launches of dummy and later live ASMPs were performed using the Mirage IV as the launch platform between 1981 and 1983.