In 1980, a research program was undertaken to study further improvements to the Leopard 1, providing it with a completely modern fire control system and fully effective night/bad-weather vision system. The decision was made to base the upgrades on the earlier models, which were no longer competitive.
The resulting Leopard 1A5 was based on 1,225 vehicles of the Leopard 1A1A1 model. The turrets were again modified for the 1A5, both in order to store all of the new equipment, as well as to move more of the ammunition into the rear of the turret, as opposed to the left side of the driver where it had previously been stored. The new turret was also able to mount the newer 120 mm gun from the Leopard 2 if desired, although this option has not been used.
After trials, the Krupp-Atlas Elektronik EMES 18 fire control system, which was developed from the EMES 15 used on the Leopard 2, was selected in December 1983. The EMES 18 included two new sights on the top of the turret, and no longer required the "bumps" as did the earlier optical systems. A crucial part of the upgrade was the introduction of more effective ammunition, including new APFSDS rounds.
The Leopard tank could also be fitted with bolt-on lexan armour panels, which have increased the effectiveness of the armour. These "modified" tanks have proved themselves in the field.
The first modified vehicle was delivered in early 1987. Since then, almost all users of the Leopard 1 have also applied similar changes to their own vehicles, and in most ways the 1A5 can be considered the "standard" Leopard 1 today.