The great powers post-war policy was intimately linked to oil, in particular to Middle East oil. It was no longer individual businessmen but governments who were now involved in the fight for control of oil in the Middle East. Oil had become an essential part of national strategies. The American oil companies had a vital role in the slow process of defining, on the part of the American government, a real international oil policy. In this way they opened up the way to United States political and economic involvement in the Middle East, a region which until the outbreak of the Second World War had been considered a European sphere of influence. After the Second World War, Washington elaborated a foreign defence policy for the Middle East, capable of defending American interests in the region. The strategic importance of oil and the huge potential of the Arab oil reserves acquired new meaning in the context of the Cold War, they contributed to defening the system of access to resources, an element of utmost importance to American and Western security.