See subject.
Also: what is he doing at the moment of the photo?
Also also: does this soldier have special training, and so, there are x number of them for [insert unit name here]? Similarly, he’s not called “the mortar-ist” or “mortar-guy,” right, like “a sniper,” or whatever? (Which leads me to think it would be part of training for everybody…, maybe…)
I don’t know what the thing on his wrist is, but as for what he’s doing, I’m going to guess ‘nothing in particular’. Going by the smoke, I’m assuming the gun just went off, so he’s probably not assembling it. It almost looks like he’s leaning on it and the photog just caught him with his head down for a split second for no real reason and liked the shot so he published it.
ETA, if you look at how his glowsticks are swinging, I’m going to guess right before this shot was taken he was standing and this was as he was kneeling down. I’ll bet he grabbed the muzzle on his way down just to steady himself and soften the landing on his knee. The same way anyone would if they were about to kneel down like that and they were near something they could put their hand on.
It looks to be some kind of firing solution calculator. And no not everyone knows how to fire a mortar it is a specialized job skill which a Mortarman go to school for. Or as they are more commonly known: Mortar Maggots.
Actually it looks like he just fired the weapon. To fire a mortar round you drop it down the tube and look down so the flash doesn’t get you in the face.
Makes sense, but would you have your hands on it when it’s firing or would it get too hot?
I have no idea how hot something like that gets and how rapidly you can fire it.
Keeping one’s head down as the mortar fires (especially if the eyes are unavoidably level with the muzzle) seems to be the practice. But holding the tube isn’t. In field artillery, touching the piece during sighting and firing is a no-no.
Yeah but you don’t drop a 155 down the muzzle either.
obviously, he is Tebowing. 
I’m no mortarman…But it looks to me that joey in post#2 is correct.
The only mortar I’ve ever fired was to launch flares into the nightime sky, so precise aiming wasn’t important. And we did keep one hand on the barrel of the mortar (which had a heat-proof pad to protect your hand.)
The soldier is wearing something on that harness on his back with an antenna folded into an upside down “U” sticking out. He could be receiving some sort of targeting information on that unit and the wrist-piece is the readout/control for it. It doesn’t look to me like that mortar has much of a baseplate. But if it’s enough, it’s enough.
Are those regulation shoes?
I was going to say Garmin GPS - looks pretty similar to mine (except mine is much older). I don’t know if it would be standard issue kit, though.
Never been anywhere near one, outside an open base exhibit, but it looks like he is looking down at the bubble, adjusting for effect. I assume thats what the black rectangular thing at the base of the tube.
Declan
Yeah, I noticed that too. That seems quite unusual for the military outside PT. Sneakers?!?
Then again, he seems to be wearing the old, non-digital uniform.
I’m not understanding the uniform at all. Nothing he is wearing is standard. The sneakers. Unbloused pants. Old BDU style uniform pattern but with a shoulder pocket that the old uniforms didn’t have. An odd CVC helmet instead of a Kevlar. Maybe special ops? But the lack of the standard beard confuses me.
Mortarman is the correct term. In the Army it is actually part of the Infantry Branch not Artillery. A basic infantryman is a 11B. A motorman is 11C. The official term is Indirect Fire Infantryman. Not everyone knows how to fire a mortar. Its a very specialized skill.
The thing on his wrist is a GPS. Nothing more fancy than that.
Firing a 60mm mortar. Hasty, direct-lay shot. Hes probably in contact with the enemy in that photo.
Yes he has special training. Not only does becoming a mortarman require specialized training, this is not a conventional soldier, so he bas had more advanced special operations training. He looks to me to be MARSOC.
And what’s up with the lady or child’s house slipper to right? Where the hell is this?
He is almost certainly MARSOC.
Welcome to Afghanistan. I once had a lady nearby hanging her laundry on the line during a fire fight. Didn’t even bother going back in the house.
…did a reverse google image search: and according to this caption the soldier is US Special Forces. So I just assume they can wear whatever they damn like. 
(Although that is simply a WAG)