During the Cold War, Japan defined its security policy by the Yoshida Doctrine — maintaining a low profile security posture while relying on the United States for protection based on the US–Japan Security Treaty.
There was little appetite within Japan’s government or military for military-to-military relationships with other regional states. Yet the past three decades have seen a steady diversification of Japanese security partnerships, including with South Korea, Australia and India as well as with some ASEAN and European countries. Notably, these relationships were not meant to replace the still-dominant security reliance on the US–Japan alliance, but instead were part of a strategy — carried out in tandem with the US — which saw the two states moving away from its strict bilateralism to what Michael J. Green calls ‘federated capabilities’.
Read more in International Affairs.