Five Power Defence Arrangements

The Five Power Defence Arrangements (FPDA) are a series of bilateral defence relationships established by a series of multi-lateral agreements between the Commonwealth countries Australia, Malaysia, New Zealand, Singapore, and the United Kingdom. Signed in 1971, the FPDA consists of the five powers consulting each other "immediately" in the event of threat or an armed attack on any of the FPDA members for the purpose of deciding what measures should be taken, jointly or separately in response.

Source: Wikipedia — Five Power Defence Arrangements (CC BY-SA 4.0)