pvp

[airmanone]

when someone attacks do you lose your troops permanently that was killed during PVP?

[Konstantin Fomenko]

You do - so it makes sense to pull out the injured battalions out of the fight, or have healer units - like your hero, enchanter, foot knight, goblins e.t.c.
Keep in mind - the PvP rewards - both the gold loot and Crown points outweigh the value of lost troops.