What do you guys mean by "no losses"?

[Kathos]

A No-Loss campaign means that throughout the game at the end of a battle you have 0 units lost, you leave with the exact same amount that you walked in with. Summons do not count as they are not permanent creatures, and resurrecting units in the battle (paladins, inquisitors, ressurection order magic) is a viable and actually necessary to complete. If you check the high scores and look at battle statistics one of the stats shown is units lost in battle. The objective of a No-Loss Impossible campaign is to have a 0 by the time you finish the game. It is not impossible, but it is very hard at times and requires some innovative thinking as some battles, typically with heroes, can be quite frustrating.