Kind of hazy about his military experience (spoilers)
I was a little confused about the Afghanistan military experience Statham's character had.
It sure looked to me, based on the aerial footage and radio chatter like they were the victims of some kind of friendly fire incident -- they seemed like they got hit with some kind of fire from a gunship, like a 30mm gatling gun based on the way the fire seemed to come from above, which for a lot of reasons (weapons, tactics, etc) doesn't seem like Taliban. An IED might make sense, but it would have killed Statham, too, or at least done damage differently than was experienced.
The other scenes just show Statham leading some Afghani through the streets and then presumably executing him, all of which seemed kind of disconnected from the APC incident, although it was made pretty clear through the movie that he was just some guy Statham decided to waste in retaliation.
Initially I was kind of expecting Statham to be a drunk because he was wronged by the military (friendly fire, etc)and not because he decided to freelance on some civilian, although that was the real reason.
Overall it was an OK movie, although like others I was kind of expecting more of a typical Statham action picture, but I wish the Afghanistan bit had been better spelled out than "Afgahnistan is the suck."