British spy chiefs secretly warned that the United States would be prepared to invade Saudi Arabia and Kuwait to seize their oilfields following the 1973 Arab-Israeli war, it was disclosed Thursday.
Files released to the British National Archives under the 30-year rule for classified documents show the intelligence agencies believed the US was ready to take military action to prevent further disruption to oil supplies.
It followed the decision in October 1973 by the Arab nations to slash oil production, and send prices rocketing, while imposing a complete embargo on the Americans over their support for Israel.
In Britain, Prime Minister Edward Heath's Conservative government, which adopted a more pro-Arab line, was forced to draw up plans for gasoline rationing after panic buying led to shortages at filling stations.
Although the war in the Middle East was over after three weeks, a secret assessment drawn up for government ministers by the Joint Intelligence Committee (JIC) - including the heads of MI5 and MI6 - concluded the US would rather risk military action than be held to ransom again by the Arabs.
The report, dated December 12, 1973 and marked "UK Eyes Alpha", described the seizure of the oil-producing areas in the region as "the possibility uppermost in American thinking".
The JIC calculated the US could guarantee sufficient oil supplies for themselves and their allies by taking the oilfields in Saudi Arabia, Kuwait and the Gulf state of Abu Dhabi, with total reserves of more than 28 billion tons.
It warned the American occupation would need to last 10 years, as the West developed alternative energy sources, and would result in the "total alienation" of the Arabs and much of the rest of the Third World, as well as "domestic dissension" in the United States.
However, it said the Republican administration of President Richard Nixon could be prepared to take the risks, if it was faced with the "dark scenario" of renewed Arab-Israeli conflict and further protracted oil restrictions.
It said that the United States would even consider pre-emptive action if Arab governments, "elated by the success of the oil weapon," began imposing new demands.
"Even if this had not happened, the US government might consider that it could not tolerate a situation in which the US and its allies were in effect at the mercy of a small group of unreasonable countries," it said.
"In view of the incalculable consequences of military action against the Arabs, we consider that US intervention would probably come late as a move of last resort," it said.
"But we cannot rule out the possibility of a rather earlier intervention," it added.
The JIC said that the initial US invasion force would not have to be large, with two brigades to seize the Saudi oilfields and one brigade each to take Kuwait and Abu Dhabi.
In order to maintain the element of surprise, the Americans' first choice would probably be an airborne assault, but if that proved impracticable they could send an amphibious task force.
"For Saudi Arabia, the operation could be fairly straightforward. The peacetime garrison of Dhahran is one lightly armed National Guard battalion and a Hawk SAM battery," it said.
"The initial assault could be made by a brigade tasked to knock out the Hawk battery, seize the airfield, and so far as possible prevent sabotage to the oilfields."
"For Kuwait the operational problems are greater. The Kuwaitis have about 100 tanks, mostly concentrated near the airport. This means that although the initial assault could still be made by a brigade, the assault force would need to be rapidly reinforced, say within six hours, by tanks of its own."
A "complication" in the case of Abu Dhabi was the presence of some seconded British officers in the Abu Dhabi Defence Force, and for this reason, the JIC said that the Americans could ask Britain to carry out that operation.
The Americans would almost certainly also ask to use the British staging facilities at Gan or Diego Garcia, in the Indian Ocean, it said.
The JIC said that the US would probably give the Soviet Union prior notice of its intentions, and that Kremlin opposition would "probably stop short of direct military intervention".
However, in a reversal of what was actually to happen 18 years later, the JIC said that if the Americans seized Kuwait, Iraq may try to mount a counter-invasion to expel them.