During this period Australia continued to retain forces in Malaysia as part of the Five Power Defence Arrangements ( FPDA ) agreed in 1971 to defend it in the event of external attack , with this commitment initially including significant air , ground and naval forces . However , these forces were gradually reduced with the infantry battalion withdrawn from Singapore in 1973 , and the two Mirage fighter squadrons in 1988 . Since then a detachment of Orion maritime patrol aircraft , support personnel , and an infantry company known as Rifle Company Butterworth have been maintained , as well as occasional deployments of F / A @-@ 18 Hornet fighter aircraft . Australian submarines were reportedly also involved in a number of clandestine surveillance missions throughout Asian waters in the last decades of the Cold War . Airforce and Navy units were also involved in tracking Soviet ship and submarine movements in the region . Since then the Orions have continued to participate in maritime security operations as part of Operation Gateway , conducting patrols over the Indian Ocean , Strait of Malacca and South China Sea . They have reportedly also been involved in freedom of navigation flights .