That's why it's an anti-war game, really, because it engages with the mechanics of war - the raw, bleeding actions of it freed from notions of grandeur and honour - on a visceral level. It gives you means and a motive to kill and then knocks the motive away from you as hard as it can to see if you'll keep on killing because the means remains.
And once you've accepted that your actions have no meaning other than snuffing out other living beings from your country, with your ideologies and fears, who might have even gone to the same school as you, it asks you why you're doing it and you can't answer the question.
Walker becomes the invading soldier, the gore-streaked face of anarchy that we've all been taught to fear. His actions against America - and the West - are personal. This isn't the grass-roots guerrilla actions of Homefront, the embittered defence of Resistance or the defence of the realm in Command & Conquer: Red Alert. The enemy is not a faceless and unknowable and evil.
There's no clear separation between good and evil, no grand plans to take over the world that must be thwarted by our brave boys. This is men far from home killing each other for reasons they can't understand or remember. This is conflict as a free-standing reality, not a means to an end.
The developers of Spec Ops: The Line have created a seven-hour masterpiece that dumps you into a conflict and slowly reveals the reality of what you're doing whilst making sure you have fun doing it. It's a near-perfect exercise in doublethink, riddled with acts both proud and shameful.
The Line can get a little preachy at times, but only rarely - it doesn't want to say that the reasons for war are bad. It doesn't want to say that soldiers are bad people. It just wants to make you feel - as keenly as possible without putting an M16 in your hand and sending you to the frontline - what the violent actions of these men and women are when stripped of political meaning.