Tony Karon writes: President Barack Obama’s announcement on Friday that all 40,000 U.S. troops still in Iraq will leave the country by New Year’s Eve will, inevitably, draw howls of derision from GOP presidential hopefuls — this is, after all, early election season. But the decision to leave Iraq by that date was not actually taken by President Obama — it was taken by President George W. Bush, and by the Iraqi government.

In one of his final acts in office, President Bush in December of 2008 had signed a Status of Forces Agreement (SOFA) with the Iraqi government that set the clock ticking on ending the war he’d launched in March of 2003. The SOFA provided a legal basis for the presence of U.S. forces in Iraq after the United Nations Security Council mandate for the occupation mission expired at the end of 2008. But it required that all U.S. forces be gone from Iraq by January 1, 2012, unless the Iraqi government was willing to negotiate a new agreement that would extend their mandate. And as Middle East historian Juan Cole has noted, “Bush had to sign what the [Iraqi] parliament gave him or face the prospect that U.S. troops would have to leave by 31 December, 2008, something that would have been interpreted as a defeat… Bush and his generals clearly expected, however, that over time Washington would be able to wriggle out of the treaty and would find a way to keep a division or so in Iraq past that deadline.”

But ending the U.S. troop presence in Iraq was an overwhelmingly popular demand among Iraqis, and Prime Minister Nuri al-Maliki appears to have been unwilling to take the political risk of extending it. While he was inclined to see a small number of American soldiers stay behind to continue mentoring Iraqi forces, the likes of Shi’ite cleric Moqtada al-Sadr, on whose support Maliki’s ruling coalition depends, were having none of it. Even the Obama Administration’s plan to keep some 3,000 trainers behind failed because the Iraqis were unwilling to grant them the legal immunity from local prosecution that is common to SOF agreements in most countries where U.S. forces are based.

So, while U.S. commanders would have liked to have kept a division or more behind in Iraq to face any contingencies — and, increasingly, Administration figures had begun citing the challenge of Iran, next door — it was Iraqi democracy that put the kibosh on that goal. The Bush Administration had agreed in 2004 to restore Iraqi sovereignty, and in 2005 put the country’s elected government in charge of shaping its destiny. But President Bush hadn’t anticipated that Iraqi democracy would see pro-U.S. parties sidelined and would, instead, consistently return governments closer to Tehran than they are to Washington. Contra expectations, a democratic Iraq has turned out to be at odds with much of U.S. regional strategy — first and foremost its campaign to isolate Iran.