He encountered the enemy on the battlefield.

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.

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.

Paying the urban planning tax is a citizen's duty.

The United Nations Environment Programme is providing solutions to global environmental problems.

We should always remember the power of Kannon in difficult times.