The US is the dominant power in the Middle East. Between 1946 and 1991, the US gradually became the dominant power in the region to defend against Soviet influence, maintain regional stability, and ensure the flow of oil from the Persian Gulf to the world economy. American interests in the Middle East were public interests of the states in the American-led order. The US had an obligation to guarantee these interests as a liberal hegemon, yet it occasionally used methods consistent with imperial powers to provide these public goods. The US tried to use a collective security organization, covert action, and the hub and spokes method, with Britain, Iran, and Israel, to maintain these interests without a direct American presence. However, these efforts failed to achieve American interests in the Persian Gulf. As a result, the US developed the capacity to project force into the Gulf. This capability became a permanent military presence after the Iraqi invasion of Kuwait in 1991, when new efforts to create a regional security organization failed. In the Levant, Israel guaranteed American objectives and the US never had to create a large military presence in the sub-region.