bridgehead

noun

a defensive post at the end of a bridge nearest to the enemy
敵に一番近い橋梁の端に作る防御用とりで
an area in hostile territory that has been captured and is held awaiting further troops and supplies
一層の軍と供給を待ちながら捕捉されて、保持される敵地の領域
- an attempt to secure a bridgehead behind enemy lines
  敵の布陣の後ろに橋頭堡を確保する試み
- the only foothold left for British troops in Europe was Gibraltar
  ヨーロッパにおける英国軍のために残った唯一の足場は、ジブラルタルであった