The Carter Doctrine was a policy proclaimed by President of the United States Jimmy Carter in his State of the Union Address on January 23 1980, which stated that the United States would use military force if necessary to defend its national interests in the Persian Gulf region.
The doctrine was a response to the 1979 invasion of Afghanistan by the Soviet Union, and was intended to deter the Soviet Union—the Cold War adversary of the United States—from seeking hegemony in the Persian Gulf.
After stating that Soviet troops in Afghanistan posed “a grave threat to the free movement of Middle East oil,” Carter proclaimed:
The region which is now threatened by Soviet troops in Afghanistan is of great strategic importance: It contains more than two-thirds of the world’s exportable oil.
The Soviet effort to dominate Afghanistan has brought Soviet military forces to within 300 miles of the Indian Ocean and close to the Straits of Hormuz, a waterway through which most of the world’s oil must flow. The Soviet Union is now attempting to consolidate a strategic position, therefore, that poses a grave threat to the free movement of Middle East oil . . . .
Let our position be absolutely clear: An attempt by any outside force to gain control of the Persian Gulf region will be regarded as an assault on the vital interests of the United States of America, and such an assault will be repelled by any means necessary, including military force.
This last, key sentence of the Carter Doctrine, was written by Zbigniew Brzezinski, President Carter’s National Security Adviser. Brzezinski modeled the wording of the Carter Doctrine on the Truman Doctrine, and insisted that the sentence be included in the speech “to make it very clear that the Soviets should stay away from the Persian Gulf.”