The British defence guarantee ended following Britain's decision in 1967 to withdraw its forces east of Suez, and was replaced in 1971 with the Five Power Defence Arrangements (FPDA) by which Britain, Australia, New Zealand, Malaysia and Singapore agreed to co-operate in the area of defence, and to "consult" in the event of external aggression or the threat of attack on Malaysia or Singapore. The FPDA continues to operate, and the Five Powers have a permanent Integrated Area Defence System based at RMAF Butterworth, and organise annual naval and air exercises.