primary invader

例句：

1. 1. The government is concerned about the primary invader of its borders.
   政府对边境的主要侵略者感到担忧。
2. 2. The primary invader was a group of foreign soldiers.
   主要的侵略者是一群外国士兵。
3. 3. The primary invader has been identified as a group of militants.
   主要的侵略者被确认为一群激进分子。