The M1 entered production in 1979, with the first production version M1 leaving the factory floor in February 1980. Production of the M1 continued until 1985, with an improved M1IP version being produced briefly between 1984 -1986. By 1985, several thousands of M1s had already been manufactured and put into service. In August 1985 however, the M1 was outfitted with the license-built version of the Rheinmetall 120mm gun, as found on the Leopard 2 tank and subsequently entered production as the M1A1 Abrams. Following this modification, earlier M1 units would progressively be upgraded to M1A1 standard. The M1 Abrams saw the most active service with US forces primarily in operations in the Middle East, but known operators also include Australia, Kuwait, Saudi Arabia, Egypt and others. Nonetheless, the American M1 Abrams is one of the most successful and widely fielded modern-day MBTs in use anywhere in the world, and rightfully deserves its iconic status alongside other American legends such as the M4 Sherman and M60 Patton, to name but a few. The fact that the M1 Abrams is still being manufactured and used today, almost four decades after its introduction, serves as a testimony to that statement.