Ambush

"Ambush is a special combat action you can take. When you put a character into Ambush, they will not attack or make any further moves that turn. However, they gain the ability to interrupt and attack during the enemy's own turn when the next enemy enters attack range. This can be an effective tactic when you want to lure the enemy into your crossfire. When a character is in Ambush mode, an icon will appear above their head. Remember that enemies can use Ambush too!"

- Desert Rangers Training Regulations 0.0036

Ambush is a tactic available if positioning is good and you'd rather wait for the enemy to come to you, allowing you to create killboxes or greet knife-wielding madmen with a hail of bullets.

To set a Ranger to Ambush mode, click the Ambush button on the Combat HUD and end the Ranger's turn. The Action Point cost of an Ambush is the same as the weapon's standard attack cost. It is possible to take other actions before or after setting the Ranger to Ambush mode as long as it leaves enough Action Points to perform the Ambush.

Once in Ambush mode, the Ranger will attack the first enemy that comes within range. Ambush is not directional, meaning the Ranger will keep watch in all directions rather than just the one he or she is facing. Because Ambush is executed as soon as an enemy comes within range, at the longest range, it is best done with weapons that do not suffer from ranged penalties, such as pistols, assault rifles or sniper rifles. It is not too advisable to set up an ambush while wielding explosives or other heavy weapons, unless you planned it very carefully.

Cover
Cover bonus is ignored while enemy is moving, so you can use ambush to obstruct their movement and to hit moving enemy without cover bonus.