The enemy was not reacting as he had expected.
We're going in hot, but with any luck we'll get down and out of the box before the enemy can react.
Out in front, she saw that the enemy was reacting to her father's attack.
The noise would be continuous now and, sooner or later, the enemy must react by opening fire.
They had to finish this on speed and momentum, before the enemy could react properly.
Once they began to move, their enemies reacting, it was anybody's game.
The enemy reacted properly and plastered the place with artillery fire.
Another mile or two and they actually could ram her before the enemy could react.
They made it halfway through the clearing before the enemy could react.
In order to ensure victory, you have to figure out how your enemy interprets information and reacts to the world.