I keep reading that bringing the troops home from Iraq would cause the US to lose the war.
OK, we can't have that. So, let's decide what constitutes victory, and work from there.
1) Get rid of Saddam. This was the main reason for the invasion in the first place.
Saddam's trial starts soon. Done.
2) Get rid of WMDs. Saddam had NBC weapons (nuclear, biological, chemical) which endangered America.
The country's been gone over with a fine tooth comb. The WMD were either never there, removed, or destroyed. Either way, Iraq has no WMDs. Done.
3) Rebuild country. Iraq suffered under Saddam. It needs to re-enter the global community as a free democratic nation.
Well, except for security, this is more a job for Condi and Haliburton than for the Army Corp of Engineers, much less for a mechanized infantry battalion.
4) Destroy terrorists. The military presence in Iraq is drawing all the terrorists in the world to Iraq, protecting the US.
There are a few problems with this.
a) This reduces the Army's role in Iraq to a live action Whack-a-mole with real bullets - if that. You can't stop a constantly resupplied enemy by killing them one by one. There's more of them than there is of you. Plus, it gives all the advantages to the enemy. They choose when, where, and how to engage their opponents. Very bad strategy.
b) It isn't working. Home-grown terrorists have shown up in England; America is no doubt next.
c) It's not fair to the troops. They signed up to be America's defenders, not America's human duck decoys.
In other words, it's the wrong strategy to use troops. They need a covert force - something that doesn't have "US ARMY" written all over them. Something that can sneak around the shadows and nail these guys.
Remember, terrorist cells are not armies - they are 5 guys with plastique and rifles. A SEAL team with good intel could go from place to place, killing these guys off piecemeal. Tanks cannot sneak. Send them home.
5) Rebuild Iraq's security forces.
Again, this is not a job for combat troops. They aren't supposed to be teachers. Security consultants can do the job. If they are smart enough to avoid uniforms, screen their applicants, and adopt a non-American sounding name for their organization, they should be a lot safer and less likely to be attacked.

In short, they have accomplished all they can do, and are now trying to do jobs they are ill-equipped to do, that others could do better, that do nothing but make them human targets.
It is time to replace them. This is not surrender, this is removing units unsuited for the current task, and replacing them with organizations better suited.
This is not defeat. This is strategy.