Unconscious

Unconscious is a mental status effect in XCOM 2.

Unconscious units are unable to move and act for the rest of the mission, similar to when a soldier is bleeding out. Unconscious units can be carried by other soldiers to reposition or evacuate them.

Unconscious units that are left behind during a mission that requires evacuation (such as the ADVENT Forge assault) are considered captured, though unconscious units that are not evacuated by the end of a non-evacuation mission (such as a Guerilla Op) will be revived and can be selected again for another mission (if they took damage, they will have to spend some time in the hospital).

Any attack that can Stun the target (e.g. a Stun Lancer's Stun Baton, a Muton's Bayonet or a Berserker's Devastating Blow) has a chance to knock the target unconscious, which increases as the target's health decreases. The Subdue ability, which is used on enemy VIP targets, also knocks the target unconscious. This is the only time an XCOM soldier is able to knock an enemy unconscious (other than mind-controlling enemies such as stun lancers) though the Berserker Queen's Quake ability can knock enemy units unconscious if they are caught in its area.

Unlike dead soldiers, unconscious soldiers still retain their health bar and can be damaged and healed accordingly. While unconscious units cannot be targeted, area of effect attacks will still damage them. For this reason, if you are not able to revive an unconscious soldier (and do not need to carry them to an evacuation point), the safest thing to do is to leave them behind, so they won't be hurt when your active units are targeted by AoE attacks.

Unconscious XCOM soldiers can be revived using the Specialist's Revival protocol ability.

A Psi Operative's Solace ability will prevent soldiers from becoming unconscious.

A bleeding out soldier that is Stabilized will be rendered unconscious with 1 health point.

If the objective of the map is to kill all enemies, then you don't need to revive or carry unconscious Soldiers. They will be collected once the map is cleared. If, however, the squad have to reach (or place) an EVAC zone, then you’ll need to carry any unconscious soldiers to the EVAC zone or they will be captured.