These events spurred the United Kingdom to develop a new tank gun in 1956, the Royal Ordnance L7 to keep the Centurion viable against this new Soviet tank design and the United States to develop the XM60 tank in 1957. The L7 was specifically designed to fit into the turret mountings of the 20 pounder. This would enable the Centurion tanks to be up-gunned with minimum modifications; hence, the fleet could be upgraded in a shorter time and at a lower cost.