A situation arised during the weekends play where the defenders wanted to shell a hex with a smoke marker. We all agreed that the +2 cover from smoke would be illogical since you attack the whole hex, sure the hex is obscured by the smoke but what do mortars care. We didn't find anything in the rulebook about it not being so.

Is this really so or is there an errata or anything on this I don't know about?

A mortar attack is a area attack. In the example on page 32, a mortar attack against a squad in a woods hex, the squad recieves a +2 for woods cover. I suppose you can use this as an example in that a mortar is attacking the whole woods hex just like it is attacking a whole smoke hex and that the squad would recieve the +2 cover.

old gamer said:

the difference is that trees actually stopes shrappnel and woods where smoke does not, and since you're not actually targeting units but a complete hex without any tangible cover, the shrapnel should hit with full force anyway. so my question still stands.

creepwood said:

Actually being in the woods while under mortar or artillery fire was/is a bad thing. The trees would detonate the shells in the air and send shell and tree fragments raining down on the troops.

JoeBuckeye: I'm not saying that timed fuses on mortal shells was used in the war, but it doesn't answer my question about the cover of smoke.

Then, to answer your question:

creepwood said:

Smoke gives cover vs. mortar as vs. any other attack, there's no point in the rules why it shouldn't do so. There's no errata or anything so far concerning this "issue".

You're free to make up your own rules if you dislike it.

Don't forget the modifiers for cover are also an abstraction for how visible the target is to spotters. If the target can't be seen it's harder to direct artillery/mortar fire accurately, as in the case of smoke.