In September 1999, B Squadron, 3rd/4th Cavalry Regiment was deployed to East Timor as part of the INTERFET peacekeeping mission. The unit supported light infantry units, and its M113s proved better suited to East Timor's rugged terrain and tropical climate than the 2nd Cavalry Regiment's ASLAVs, which at times were unable to operate off road due to muddy conditions. 5/7 RAR was subsequently deployed to East Timor and proved highly effective. It was found that the mechanised battalion could cover an area which had previously needed to be patrolled by several light infantry battalions. Australian M113s remained in East Timor until 2002 to support the infantry battalions deployed there. While the deployment of M113s to East Timor was considered successful, the age of the vehicles and their obsolescent communications and navigation systems proved to be a limitation; this included the absence of Global Positioning System equipment to aid navigation. There were also concerns regarding the lack of stabilisation and night sights for the vehicles' armament, and the driver being unable to use a night driving system which had a wide field of view. The M113s also proved less mechanically reliable than the newer ASLAVs, which were also better armed. The experiences gained from operating M113s in East Timor helped to validate and improve the Army's mechanised doctrine, and influenced the requirements which were set for the M113 upgrade project.