Answer: enemylines

AnswerCrossword Clue
ENEMYLINES

It's dangerous to be behind them

ENEMYLINES

Front borders

ENEMYLINES

They may be crossed in battle

ENEMYLINES
Moles may cross them
ENEMYLINES
Infiltration destinations
ENEMYLINESHostile territory is behind them
ENEMYLINESMoles go behind them
ENEMYLINESA spy will often cross them
ENEMYLINESDangerous thing to cross