In 1980, a research program was undertaken to investigate further improvements to the Leopard 1, stipulating the need for a new fire control system/ballistic computer and thermal camera for effective night and all-weather capabilities to effectively fight against the more sophisticated Soviet T-64B, T-72B and T-80B series of tanks. A crucial part of the upgrade was the introduction of more effective ammunition, including new APFSDS rounds. The decision was made to base the upgrade on earlier models which were no longer competitive. The resulting Leopard 1A5 was a retrofit of 1,225 Leopard 1A1A1 vehicles from Bundeswehr stocks.