撤出 is a separable verb (离合词) meaning 'to withdraw' or 'to pull out' — commonly used for troops, but also for personnel, resources, or positions. You can split 撤 and 出 when adding a measure word, duration, or complement: 撤了一个师 ('withdrew one division') or 撤不出来 ('cannot withdraw'). The object usually goes after 撤出 as a whole (e.g. 撤出阵地), or before it with 把 (e.g. 把部队撤出).