How severely injured does a soldier have to be before being discharged?

My sister has a former employee, “Seth”, she cares a great deal for who joined the army three years ago. He was wounded several weeks ago in Iraq when a suicide bomber (a female suicide bomber, which is very rare) approached his unit. Two Iraqis who were with them were killed and some of the U.S. soldiers were seriously wounded. Seth received wounds that I would call ‘significant’ but not life threatening; he’ll require several months of treatment for burns to his face and torso (his clothing caught on fire) but ultimately he shouldn’t have anything more serious than very minor facial scars and slightly worse scars on his body.*

For some reason (probably inaccurate movies) I assumed that once a soldier was seriously wounded (even if it’s hopefully no more permanent than mentioned) he was eligible for discharge. Apparently not as Seth is not only still in service (though stateside at the moment recuperating) but already talking about serving another T.o.D. in Iraq. How badly does somebody have to be injured before being eligible for an honorable discharge?

The army is missing a world of great propaganda with this kid [he’s about 24, actually, but I’ll say kid anyway] as 1) he’s extremely well spoken 2) he’s former football star/mom/pop/apple pie in demeanor who joined the military while the war was going on largely as an act of patriotism* 3) has a beautiful wife 4) is very good looking [looks very much like Jake Gyllenhaal] 5) has no regrets about joining the service and 6) [and most important] in addition to being a wounded vet he was a hero that day, his treatment of his fellow soldiers stopping the wounds from being far more serious if not actually saving their lives.

**True, he also joined due to economic incentives as he’s from a poor family and it’s a great way to get an education/career, but the fact he joined it knowing he’d be going to Iraq doesn’t detract from the patriotism part.

Presumably, when he is no longer fit to carry on with his duties? That would seem to make the most sense, if your army is a war fighting machine and not a welfare program, the first priority would be it’s ability to fight wars, so once you are deemed to be useless, I see no reason to let you stay on. Assuming the fellow in question actually WANTS to stay on, which, in the case of a volunteer military, would be a given.

There are guys going back to Afghanistan and Iraq with prosthetic legs.

Artificial limb technology has come quite a long way, and the military now has a policy that if a member wants to continue on active duty with an artificial leg, they can, as long as they can pass physical fitness requirements with that leg.

At least one guy requalified as a paratrooper with his new leg, and redeployed.