He answers the question immediately with an obvious answer: Obama did.

Barack Obama was a principled opponent of the Iraq War from its beginning. But when he became president in January 2009, he was handed a war that was won. The surge had succeeded. Al-Qaeda in Iraq had been routed, driven to humiliating defeat by an Anbar Awakening of Sunnis fighting side-by-side with the infidel Americans. Even more remarkably, the Shiite militias had been taken down, with American backing, by the forces of Shiite prime minister Nouri al-Maliki. They crushed the Sadr militias from Basra to Sadr City.

Al-Qaeda decimated. A Shiite prime minister taking a decisively nationalist line. Iraqi Sunnis ready to integrate into a new national government. U.S. casualties at their lowest ebb in the entire war. Elections approaching. Obama was left with but a single task: Negotiate a new status-of-forces agreement (SOFA) to reinforce these gains and create a strategic partnership with the Arab world’s only democracy.

He blew it. Negotiations, such as they were, finally collapsed last month. There is no agreement, no partnership. As of December 31, the American military presence in Iraq will be liquidated.

And it’s not as if that deadline snuck up on Obama. He had three years to prepare for it. Everyone involved, Iraqi and American, knew that the 2008 SOFA calling for full U.S. withdrawal was meant to be renegotiated. And all major parties but one (the Sadr faction) had an interest in some residual stabilizing U.S. force, like the postwar deployments in Japan, Germany, and Korea.

Krauthammer points to two abject failures leading to the liquidation/surrender in Iraq. First, he says, was Vice President Joe Biden’s total inability to broker a deal among the major factions in Iraq – the Kurds, the Sunni coalition led by former president Ayad Allawi and the Shiite coalition led by current president Nouri al-Malaki – who combined to pull 69 percent of the vote in the last round of elections on a status-of-forces agreement. All three of those factions had it in their interest for American troops to stay in Iraq to help train that country’s military and keep Iraq from being overrun by Iran through whatever means the Iranians opted for.

And Biden, who ran for president in 2008 on the idiotic notion that Iraq be broken up into three warring mini-states, mucked the job. Which is not a surprise given that Biden has failed at virtually every executive task he’s ever been given. Let’s not forget he was also in charge of making sure no stimulus money was wasted, and we got Solyndra as a result.

The second failure Krauthammer notes isn’t Biden’s but Obama’s, and it’s not borne of incompetence but ideology…

The military recommended nearly 20,000 troops, considerably fewer than our 28,500 in Korea, 40,000 in Japan, and 54,000 in Germany. The president rejected those proposals, choosing instead a level of 3,000 to 5,000 troops.

A deployment so risibly small would have to expend all its energies simply protecting itself — the fate of our tragic, missionless 1982 Lebanon deployment — with no real capability to train the Iraqis, build their U.S.-equipped air force, mediate ethnic disputes (as we have successfully done, for example, between local Arabs and Kurds), operate surveillance and special-ops bases, and establish the kind of close military-to-military relations that undergird our strongest alliances.

The Obama proposal was an unmistakable signal of unseriousness. It became clear that he simply wanted out, leaving any Iraqi foolish enough to maintain a pro-American orientation exposed to Iranian influence, now unopposed and potentially lethal. Message received. Just this past week, Massoud Barzani, leader of the Kurds — for two decades the staunchest of U.S. allies — visited Tehran to bend a knee to both Pres. Mahmoud Ahmadinejad and Ayatollah Ali Khamenei.

The factor most often given for the pullout is that the Iraqis wouldn’t provide immunity for American troops in theater. But Obama’s predecessor managed to negotiate that; it’s instructive that Obama couldn’t.

American influence in the Middle East is at its lowest ebb ever. Consider that when Obama took office in 2009 the Iraq War was won and the Iranian government was teetering on the edge; by June of that year more than a million Iranians were in the streets looking for a regime change. That positive momentum has been absolutely squandered. Obama’s major accomplishments in the region over the last three years include the changing out of the Qaddafi regime in Libya, a regime we had normalized relations with and which was providing us intelligence, for an Islamist theocracy aligned with Al Qaeda, abandoning a staunch, if imperfect, ally in Egypt in exchange for the Muslim Brotherhood taking control and wiping away peace with Israel, and now the abandonment of Iraq to its fate as a vassal state of Iran.

Naturally, there will be sinister consequences for this leadership failure. Obama won’t likely bear them; by the time the full effect of our defeat in the region hits home he’ll be earning millions on the rubber-chicken circuit and besting Jimmy Carter as the country’s leading ex-president who dislikes its people. Instead, the country itself will suffer those consequences.