。
The soldiers all had maps of the area.
Literal
Soldiers [topic-は] all that area's map [object-を] had.
兵隊達 uses 達 as the plural suffix for 'soldiers.' 全員 means 'every member/all of them.' その地帯の地図 is 'maps of that area.' 持っていた is the past progressive of 持つ — 'were carrying/had.' A military context sentence.