He moved agilely to avoid the enemy bullets.

The enemy aircraft invaded our airspace.

We are ready to invade enemy territory.

We are conducting training to devise strategies against hypothetical enemies.

The enemy general is approaching our camp.

Enemy troops are approaching our position.

He experienced his first encounter with the enemy on the battlefield.

He encountered the enemy on the battlefield.

He likes to take a walk in the park at dusk.

Linear programming is a part of operations research and is used to find the optimal solution.