Quadrilateral Security Dialogue

The Quadrilateral Security Dialogue (QSD, also known as the Quad) is an informal strategic dialogue between the United States, Japan, Australia and India that is maintained by talks between member countries. The dialogue was initiated in 2007 by Prime Minister Shinzo Abe of Japan, with the support of Vice President Dick Cheney of the US, Prime Minister John Howard of Australia and Prime Minister Manmohan Singh of India. The dialogue was paralleled by joint military exercises of an unprecedented scale, titled Exercise Malabar. The diplomatic and military arrangement was widely viewed as a response to increased Chinese economic and military power, and the Chinese government responded to the Quadrilateral dialogue by issuing formal diplomatic protests to its members.

The QSD ceased following the withdrawal of Australia during Kevin Rudd’s tenure as prime minister, reflecting ambivalence in Australian policy over the growing tension between the United States and China in the Asia-Pacific. Following Rudd's replacement by Julia Gillard in 2010, enhanced military cooperation between the United States and Australia was resumed, leading to the placement of US Marines near Darwin, Australia, overlooking the Timor Sea and Lombok Strait. India, Japan, and the United States continue to hold joint naval exercises through Malabar. During the 2017 ASEAN Summits, all four former members rejoined in negotiations to revive the quadrilateral alliance.

In Manila, Prime Minister Malcolm Turnbull of Australia, Prime Minister Shinzo Abe of Japan, Prime Minister Narendra Modi of India, and President Donald Trump of the United States agreed to revive the security pact in order to confront China militarily and diplomatically in the South China Sea. A 2021 joint statement, "The Spirit of the Quad," emphasises the shared vision for a free and open Indo-Pacific, the rules-based maritime order in the East and South China Seas, and pledge to respond to the economic and health impacts of COVID-19.