 In 1967 , the German Ministry of Defense decided to re @-@ open a Leopard 1 improvement program , known as the Vergoldeter Leopard ( " Gilded Leopard " ) , later renamed the Keiler ( " Wild Boar " ) . Krauss @-@ Maffei was chosen as the contractor , and two prototypes were developed in 1969 and 1970 . This program grew into the Leopard 2 ; the first prototype of the new tank was delivered in 1972 , equipped with a 105 @-@ millimeter ( 4 @.@ 1 in ) smoothbore main gun . Between 1972 and 1975 , a total of 17 prototypes were developed . The new 120 mm gun 's ten @-@ year development effort , which had begun in 1964 , ended in 1974 . Ten of the 17 turrets built were equipped with the 105 mm smoothbore gun , and the other seven were equipped with the larger 120 mm gun . Another program aimed to mount the 152 @-@ millimeter ( 6 @.@ 0 in ) missile @-@ gun was also developed in an attempt to save components from the MBT @-@ 70 , but in 1971 the program was ended for economic reasons . Instead , the Germans opted for Rheinmetall 's 120 mm L / 44 smoothbore tank gun . 
