On October 6, 1973, Egypt attacked the Bar Lev Line in the Sinai Peninsula and Syria launched an offensive in the Golan Heights, both of which had been occupied by Israel during the 1967 Six-Day War. On October 12, 1973, US president Richard Nixon authorized Operation Nickel Grass, a strategic airlift to deliver weapons and supplies to Israel in order to replace its materiel losses, after the Soviet Union began sending arms to Syria and Egypt. The following day, on October 17, Arab oil producers cut production by 5% and instituted an oil embargo against Israel's allies: the United States, the Netherlands, Rhodesia, South Africa, and Portugal. Saudi Arabia only consented to the embargo after Nixon's promise of $2.2 billion in military aid to Israel. The embargo was accompanied by gradual monthly production cuts—by December, production had been cut to 25% of September levels. This contributed to a global recession and increased tension between the United States and its European allies, who faulted the US for provoking an embargo by providing assistance to Israel. OAPEC demanded a complete Israeli withdrawal from all territories beyond the 1949 Armistice border.