This article, with balance-of-fear theory, explains the puzzling triangular dynamics of Korea-Japan-U.S. relations in the early Cold War period. Glenn Snyder’s concept of “alliance security dilemma” associated with abandonment/entrapment fears among allies, though useful, is not enough for explaining alliance/alignment politics among states. This article additionally employs two more fears: fear of deterrence failure between enemies and fear of losing autonomy between allies. Each state’s main incentive for supporting (or increasing commitment to) the alignment partner(s) can be abandonment fear (or fear of deterrence failure) while each state’s main incentive for defecting from (or decreasing commitment to) the alignment partner(s) can be entrapment fear (or fear of losing autonomy). For instance, during the Cold War period the U.S. concern for Korea and Japan is mainly due to the former’s fear of deterrence failure —the possibility of the Communist conquest of the Korean peninsula and Finlandization of Japan — rather than the former’s fear of being abandoned by South Korea or Japan. Meanwhile, South Korea and Japan’s concern for the United States is largely due to their abandonment fears regarding the United States. Japan played a game of balancing between fear of deterrence failure regarding South Korea and abandonment fear regarding the United States; South Korea played a game of balancing between abandonment fear regarding the United States and fear of losing autonomy regarding Japan. The mechanism of balance of fears of four kinds reasonably explains triangular dynamics in the early Cold War period and, arguably, has potential to be utilized for analyzing other states’ relations in general.