How to assault an enemy unit?

[Indigo121]

I'm new to this game, I'm playing against the AI, and what I'm seeing so far is that defending units always shoot first, and what happens often is this scenario:

I know there is an enemy unit in some hex, but I don't have LOS to it. So I move the unit towards it (one hex at a time, if that makes a difference?) but the moment I get into LOS the enemy shoots my unit, often inflicting heavy damage and making it retreat.

I can use smoke but that just postpones the moment I need to get into the LOS, and I can't shoot with Z blind fire because, again, I don't have a LOS. I can use artillery but that takes forever and is usually ineffective.

It feels like there is some ultra punishing ambush mechanic in every engagement in the game. Surely in a battlefield units communicate and the attacking unit can know there is an enemy there if the HQ sees it?

Maybe I should disable Op fire in the options? Is that relevant? I don't want to lose realism, but it's getting frustrating. Even if my infantry unit gets inside a building from the safe side, I still get hammered. Is there a way to maybe edit or tone down the ambush mechanics?

Thanks