Hey Mathias, don't worry and thanks for testing this mission too.
The hill (the enemy mortar battery) is defended by AA guns - in the newest version only one AA gun, because the two guns was extremly hard - so the airstrike is not an option in the story (in the game, it would be too easy to call a strike). In the story the artillery is in move in a new setup position (when you capture the top of the hill, the arty is available on next tartget).
You have infantry support! There are two in-map squads, advancing with you, climb up to the hill and waiting for you if you late... And when you are close top the top they attack with you. (If you was too fast, they could be late). And there is two more (spawned) units, if the two in-map units eliminated, they spawned and advance to the top to help you.
When you capture the mortar battery and got the new objective to capture Khelm, these support squads advance to Khelm too. And a few minutes later two spawned units also advance to Khelm from the top of the hill and a lot of supporting squads (BMP-3s and infantry) advance from the original starting position (Kransostav?) to Khelm.
Your arty support don't need laser designator, you can use the simple mapclick to positioning the arty strike, but it's a SADRAM strike (effective against armor, not infantry), so you have to eliminate the enemy armors with it to defend your BMP-3s and - if you are very weak - let your support teams to finish the job.
To complete your objective, you have to enter Khelm, but you have not to participate in this fight, if you don't want.