Carter Doctrine

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 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.
This situation demands careful thought, steady nerves, and resolute action, not only for this year but for many years to come. It demands collective efforts to meet this new threat to security in the Persian Gulf and in Southwest Asia. It demands the participation of all those who rely on oil from the Middle East and who are concerned with global peace and stability. And it demands consultation and close cooperation with countries in the area which might be threatened.
Meeting this challenge will take national will, diplomatic and political wisdom, economic sacrifice, and, of course, military capability. We must call on the best that is in us to preserve the security of this crucial region.
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.”