Similarly, the United States, adhering to the logic of the domino theory, feared that
the fall of any one Southeast Asian state to communism would lead an adjacent state,
and eventually an entire region, to capitulate to communism. The Americans then
regarded Thailand, the only independent country in Southeast Asia with a relatively
stable economy and government, as the fortress against communist expansion into the
region. With their complementary foreign policy objectives, Thailand soon became the
most important American ally in mainland Southeast Asia.