In an effort to reduce the speeds generated at Le Mans and other fast circuits of the day by the unlimited capacity Group 6 Prototypes such as the 7 litre Fords, and to entice manufacturers of 3 litre Formula One engines into endurance racing, the Commission Sportive Internationale (then the independent competition arm of the FIA) announced that the new International Championship for Makes would be run for Group 6 Sports-Prototypes limited to 3 litre capacity for the four years from 1968 through 1971.