“撤军”常见的英文表达是 withdraw troops 或 pull out troops 。
withdraw troops：“withdraw”有“撤回、撤离”之意，“withdraw troops”即表示将部队从某个地区撤回，是比较正式和常用的表达。例如：The government decided to withdraw troops from the conflict zone.（政府决定从冲突地区撤军。）
pull out troops：“pull out”也有“撤出、离开”的含义，“pull out troops”同样表示撤军的行为。例如：The commander ordered to pull out troops immediately.（指挥官下令立即撤军。）