What are QUAD countries?

The Quadrilateral Security Dialogue (QSD), colloquially the Quad or QUAD, is a strategic security dialogue between Australia, India, Japan, and United States that is maintained by talks between member countries. The dialogue was initiated in 2007 by Japanese Prime Minister Shinzo Abe, with the support of Australian Prime Minister John Howard, Indian Prime Minister Manmohan Singh, and U.S. Vice President Dick Cheney. 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, calling it "Asian NATO".