Well do want to download Add-ons, or make AI in game do it?
I would down load the CoC add-on Unified Artillery script from them.
The Web-site is cool looking. It almost looks like ya stumbled into a Real Military site. Anyway in that add-on there is Motars you can put in and lots of other cool stuff. If ya do download it, may I suggest you do the tute as given. They talk to ya while you watch. Then you should make a map and play around with it, before putting into a mission.
http://www.main.thechainofcommand.net/If want Ai to do it with no add-ons then grab a guy, West
name him motar1(or what ever),
Intialization line : removeweapons this; this addweapon "m16grenadelauncher"; this addmagazine "Motar". ( as many as this guy can hold). Then group a couple of these guys together, set them up in various places. With-out going into scripts you can use probability of presences a little futher down on the screen of guy to have random like settings. Set the motar men to a trigger or whatever.
I always like name a guy that ya modify like that, lot iof times you end up going back to him. Secondly you take weapon away start
new. Thirdly I believe that you can add a few more motars this way to the guy, not sure though. I dont think East has a Motar guy that comes with game, but you can use the same process just use the AK74grenadelauncher instead.
The syntax may not be right. Remeber Look in the comref for weapons and script commands like "addweapon".