Britain has had a hard time keeping up with modern tank technology. Even though Britain was responsible for many of the latest developments in armor and gun technology, it is hampered by having a small army (so it can't buy many tanks for it's own use) and difficulty in selling many tanks overseas. Britain's energetic and prolific development of tank design innovations has led to it's producing three generations of tanks in the past two decades. The Khalid was a uniquely British development, a tank designed and manufactured for a foreign customer. Originally this was the Shir tank for Iran. When the 1979 revolution cancelled that contract, Jordan took over the contract. The name was changed to Khalid, some design changes were made and 274 were delivered. At this point, Jordan had better tanks than the British army, So the Khalid design was improved on (especially with the addition of British developed composite armor) and 420 Challenger tanks were delivered by the time of the Gulf War. But the Challenger was still basically a development of the 1950s Chieftain design. So the Challenger II was designed in the 1980s and entered production in the 1990s to replace the remaining Chieftains. The name is a misnomer, as the Challenger II has only about four percent commonality with the Challenger I. But the Challenger II is, next to the U.S. M1, the most capable tank in the world. Britain is in the midst of upgrading Challenger II with the same electronic goodies the latest M1 is getting. This is costing some four billion dollars (four 386 tanks). This is creating very capable tanks, but at a cost approaching low end warplanes.