Such a perimeter had little meaning when the enemy can strike from above.

We don't know where or when the enemy will strike next.

If the enemy struck from the sea, he would counter them with his own naval power.

The enemies couldn't strike at that which they could not find.

The real enemy had struck the entire world in a single night.

It is almost impossible to predict where our enemies will strike next.

Meanwhile, it was hard to see how the enemy could strike at them here.

Would you have us caught in a research project when our enemies strike?

The enemy, when he was least expected, had struck hard and was away.

Clearly the enemy has struck before I could reach my destination.