The Quadrilateral Security Dialogue, commonly known as the Quad, is an inter-governmental security forum and diplomatic partnership comprising Australia, India, Japan, and the United States. It is a loose grouping of four democracies, not a formal military alliance. The cooperation originated in December 2004 as the "Tsunami Core Group" to coordinate Humanitarian Assistance and Disaster Relief (HADR) after the Indian Ocean tsunami. The formal dialogue was initiated in 2007 by Japanese Prime Minister Shinzo Abe. The primary problem it was intended to address was the need to strengthen regional stability and respond to increased Chinese economic and political power in the Indo-Pacific. The first iteration ceased in 2008 following Australia's withdrawal.
The Quad was revived in 2017 amid renewed concerns over China's growing assertiveness. Since 2021, the grouping has elevated its engagement to annual leaders' summits. The mechanism involves high-level talks and cooperation across a broad agenda. Key areas include maritime security, health security, critical and emerging technologies, climate change, and infrastructure. Specific initiatives include the Indo-Pacific Partnership for Maritime Domain Awareness (IPMDA) for real-time information sharing. The Quad complements the Japan-led concept of a Free and Open Indo-Pacific (FOIP), aiming to secure a "rules-based order" in the region. Related military cooperation includes the joint naval exercises known as Exercise Malabar. The agenda has significantly expanded since its revival, moving beyond its initial security focus to include economic security and supply chain resilience.