In Tonga, the military's primary missions are defending Tonga's sovereignty, providing maritime security, and protecting the King; it is also responsible for humanitarian assistance and disaster relief, search and rescue operations, monitoring against illegal fishing, and delivering supplies to the outer islands; the military has contributed limited numbers of personnel to multinational military operations in Afghanistan, Iraq, and the Solomon Islands; Australia, New Zealand, and the US are key partners

Tonga has a "shiprider" agreement with the US, which allows local maritime law enforcement officers to embark on US Coast Guard (USCG) and US Navy (USN) vessels, including to board and search vessels suspected of violating laws or regulations within Tonga's designated exclusive economic zone (EEZ) or on the high seas

Tonga participated in World War I as part of the New Zealand Expeditionary Force, but the Tonga Defense Force (TDF) was not established until 1939 at the beginning of World War II; in 1943, New Zealand helped train about 2,000 Tongan troops who saw action in the Solomon Islands; the TDF was disbanded at the end of the war, but was reactivated in 1946 as the Tonga Defense Services (TDS); in 2013, the name of the TDS was changed to His Majesty’s Armed Forces of Tonga (HMAF); Tongan troops deployed to Iraq from 2004-2008 and Afghanistan to support UK forces from 2010-2014 (2025)