The jungle terrain of Borneo and lack of roads straddling the Malaysia–Indonesia border forced both Indonesian and Commonwealth forces to conduct long foot patrols. Both sides relied on light infantry operations and air transport, although Commonwealth forces enjoyed the advantage of better helicopter deployment and resupply to forward operating bases. Rivers were also used as a method of transport and infiltration. Although combat operations were primarily conducted by ground forces, airborne forces played a vital support role and naval forces ensured the security of the sea flanks. The British provided most of the defensive effort, although Malaysian forces steadily increased their contributions, and there were periodic contributions from Australian and New Zealand forces within the combined Far East Strategic Reserve stationed then in West Malaysia and Singapore.