Scouts are the weakest enemy units in the game. Any unit can destroy it with one hit. You will see a lot of them early on, but as during later stages they will be a rare sight. Scouts are the cannon fodder of The Crimson Alliance. After completing the second map, the enemy realizes that they're getting nowhere using scouts and

A Scout.

start sending more advanced troops, like tanks, stormtroopers and rocket batteries. Despite this, they still appear occasionally. Becareful not to lose track of them, as they can still pose a threat (to weakened units). They also appear quite commonly as units dropped for the enemy dropzones and can become a pain when you have to bring back an APC (the best unit for quick operations) to get rid of them.

An active scout.