What went wrong in Iraq? Well, for one thing, the whole notion of trying to use military force to create political change was fatally flawed. Even so, there were specific conditions in Iraq that guaranteed the occupation's failure and contributed to making a bad idea into a worst-case scenario, and they can all, ultimately, be traced to the state of the Republican Party.
There were several factions within the Republican Party going into the invasion, each with its own goals and methods, and they were operating at cross-purposes. Each interfered with the goals of the others, and together they succeeded in transforming a brutal but stable dictatorship into a cesspool of chaos, violence, and civil war.
(details of the train wreck below the fold)
First were the Neoconservatives, led by Paul Wolfowitz. The Neocons provided the ideological justification for overthrowing Saddam Hussein; like the Cylons, they had a Plan. The Plan was based on the reconstruction of Germany and Japan following World War II. It involved an overwhelming troop presence in post-Saddam Iraq to provide security, as was the case in Germany and Japan. Under the auspices of a benign American-run provisional military government, democratic institutions and a capitalist economy would be introduced in Iraq over a period of years, culminating in the creation of an American-sponsored democratic constitution leading to American-style democratic elections. The result, the Neocons believed, would be a supersized Middle-Eastern version of Cold War West Berlin: a beacon of democratic prosperity that would act as a siren-song to the discontented Muslim masses of the surrounding nations. The ultimate goal was to re-create the domino-style fall of Communism in Eastern Europe in 1989, except that the falling dominoes would be Middle Eastern dictatorships in Iran, Syria, Jordan, Saudi Arabia, Egypt, and Libya. Like Eastern Europe, the Middle East would be transformed into a sea of pro-American democracies.
Unfortunately for the Neocons, Secretary of Defense Donald Rumsfeld had a different reason for invading Iraq. He wanted to test out his New Model Army: a lean, mean, regime-change machine that could be dispatched anywhere in the world to carry out quick strikes against unfriendly governments. Rumsfeld's own plan for Iraq was very different from the Neocons. He wanted to go in, overthrow Saddam, set up a pro-American dictator in his place, and then withdraw within a few months. Because Rumsfeld oversaw the actual military action against Saddam, there was no overwhelming troop presence in Iraq: there were never more than 160,000 American and allied troops in Iraq, not nearly enough to maintain security in the country. As a result, order in Iraq collapsed after the fall of Saddam's dictatorship, and was never really restored. The secure conditions necessary for the Neocon Plan to work never existed. Meanwhile, the other factions prevented Rumsfeld from carrying out his own plan for a quick troop withdrawal, resulting in an extended postwar occupation of Iraq.
Unfortunately for the Neocons and Rumsfeld, Dick Cheney's reasons for overthrowing Saddam were different from both of them. For Cheney, Iraq would be an exercise in old-fashioned exploitative colonialism: a place from which large amounts of money could be extracted. It was Cheney's influence that resulted in the Iraqi Oil Ministry being the only institution in post-Saddam Iraq to be secured and maintained, and it was Cheney's influence that resulted in Americans being given preference over Iraqis when reconstruction contracts were handed out, and Cheney's own cronies at Haliburton being given preference over everyone else. This was another roadblock in the Neocon Plan: free-market capitalism in Iraq would be sacrificed for the sake of Cheney's crony capitalism.
Next, Karl Rove's reasons for overthrowing Saddam differed from everyone else's. For Rove, Iraq would be a pawn in his own grand scheme to maintain the Republican Party's control of the American government. It was Rove's influence that led to the post-Saddam provisional government, the Coalition Provisional Authority, being largely staffed with Republican Party operatives. Loyalty to the Republican Party trumped qualifications and competence. Rove, along with Cheney, also saw to it that Congressional oversight of the operations of the CPA was curtailed, to forestall the possibility that embarrassing revelations of corruption and incompetence might damage the Republican Party. This was yet another roadblock in the Neocon Plan: the creation of democratic institutions in Iraq would be stifled to allow Rove's party operatives a free hand to manipulate events for the sake of partisan political advantage back home.
Finally, George W. Bush's reasons for overthrowing Saddam also differed from everyone else's. For Bush, Iraq was simply a way for him to assert his manhood, and prove to himself that he was, too, more of a man than his father. For Bush, the continuing occupation of Iraq is evidence of his own toughness, resolution, and machismo. Withdrawal from Iraq would mean admitting defeat, and he refuses to admit defeat.
(I'm sure I must have missed a few more. Feel free to nominate your own candidates in the comments.)
This was the mix that led to the situation we find in Iraq today: a power vacuum filled by armed radical militias, a crippled economy, a ruined infrastructure, and an American occupation force far too small to control events, but doomed to remain in place indefinitely.