Permadeath?

[☆AkaAkoVT☆]

If a unit dies, is it gone for good?
Or does it revive at the end of a battle?

[your.sheepy]

I would have asked you to Google if it were not easy to spoil an important story plot.

When a soldier drops to 0 HP, he/she falls incapacitated.
Send any unit to touch them (vehicles included) to rescue them; they can be redeployed in same battle.
If you finish the mission in 3 turns, they are also rescued.

If any enemy touch them, or if 3 turns passed, they die permanently for this game.

[DoomyDoom]

There's also a "Medic Request" order, which can evacuate one incapacitated soldier from anywhere on the map during your turn, if you absolutely aren't planning on reaching him within 3 turns (or 100% can't reach now and expect enemies to step on him).

[Histidine]

Also: certain plot-important characters can't permadie, they only get forced to retreat for the remainder of the battle.

[F'xit Fastah]

Don't ya get a nice tombstone instead?

[Kevin the Inkling]

There is perma death but it's complicated.

If a soldier is killed durring a Mission. Move another one of your soldiers to their body and a Medic will be summoned, said soldier who was on the ground as a body will be fully healed and despawned. At which point you can summon them again at one of your camps.

Actual true Perma death happens under two conditions. One. The body spends more than 3 turns on the ground. Meaning anyone who was on the ground will still be alive if you finish the mission 2 turns into them becoming bodies on the ground.

Condition 2 is something you can actually ulitize to your own advantage. If an Enemy soldier moves in close to the body of a fallen soldier same point blank range as Medic spawning. Your solider will enter a dramatic cutscene and be permently dead.

However you may notice durring your Missions walking into the bodies of enemies soldiers also causes them to despawn similar in the way enemy soldiers insure perma death of on of your soldiers. This means you can ensure perma death of enemy soldiers. And if their bodies remain on the ground they can be resummoned at enemy bases. So say for example their snipers are hassling you. And keep respawning. Use a scout to ensure the enemy snipers are down for the count.

I've done this. It does actually prevent the enemy side from redeploying their soldiers. And can be a god send durring some Missions.