Nearly all of the mistakes in Iraq (including the decision to invade in the first place) were made at the political level, above the military. Bush decided to invade the country, Rumsfeld decided to commit too few troops to effectively occupy the country, and Obama decided to set a hard public deadline for withdrawal that allowed the insurgency groups that turned into ISIS to plan and bide their time.
The military can’t question the orders they receive from the president and Secretary of Defense. That’s an important part of maintaining civilian control over the military. The military can only try to carry out whatever goals and decisions they’re given by the politicians, and in Iraq the politicians (from both parties) got it wrong.
> The military can’t question the orders they receive
They can present a report on why the orders are a bad idea, IIRC. That could be seen as "questioning". And there is the possibility of disobeying illegal orders. But it is true, if the orders are legal and final then they have to be carried out. (And if they're illegal... better be prepared to prove it at a court-martial)
It’s possible there was some pushback on the manpower levels, because that actually is closer to a military decision. Though apparently even then, the military often just takes what they get. The original plans for the 1991 Gulf War didn’t include the flanking attack from the western desert because not enough forces were allocated, and it was Secretary of Defense Dick Cheney who had to remind the generals that they were allowed to request more troops if they thought they needed them.
But the decision to start and stop wars is explicitly political and there is a much greater taboo against the military trying to tell the president which wars the country should be fighting in the first place. Which is a big part of the difference between a democracy and a military dictatorship!
You forgot firing the iraq administration and the iraqy army. Im still convinced the whole thing was a plan to get a shia and sunni war going in the middle east. In that regard it was a monstrous great success.
The military can’t question the orders they receive from the president and Secretary of Defense. That’s an important part of maintaining civilian control over the military. The military can only try to carry out whatever goals and decisions they’re given by the politicians, and in Iraq the politicians (from both parties) got it wrong.