President Barack Obama faces a moment of truth soon about Iraq: Does he keep his campaign promise to pull out all combat troops by next April or his other promise to “end the war responsibly”?

[IMGCAP(1)]According to a range of military experts, including some notable critics of President George W. Bush’s policies, a sizeable U.S. presence will be necessary well into the future.

Thomas Ricks, the former Washington Post defense correspondent who exposed the failings of Bush’s initial war policy in his 2006 book, “Fiasco,” now thinks “we can’t leave” for several years.

In his new book on Bush’s 2007 troop surge, “The Gamble,” Ricks quotes the commander of U.S. forces in Iraq, Gen. Ray Odierno, as saying that at least 30,000 U.S. troops will be needed into 2014 or 2015.

Fred Kagan, the American Enterprise Institute scholar who advocated and helped design the surge, told me that, of 140,000 troops in Iraq now, “as few as possible” should be removed before Iraq’s parliamentary elections late this year and the formation of a new national government around March 2010.

Thereafter, he said, “there can be a fairly rapid withdrawal” on the 23-month schedule agreed to in the U.S.-Iraq Status of Forces Agreement reached last year.

That agreement calls for all U.S. forces to be out of Iraq by the end of 2011, but it allows for mutually agreed extensions.

Obama’s promised 16-month withdrawal schedule, Kagan said, “would mean significant withdrawals before the elections, creating tremendous risk. It would only be done to keep a campaign promise and would require renegotiating [the SOFA] with the Iraqis.”

Significantly, surge supporters like Kaplan do not declare — as some pro-Bush columnists and TV commentators do — that the U.S. has “won” the war in Iraq or “is winning.”

They concur that Iraq’s recent provincial elections achieved significant success: They were overwhelmingly peaceful. They were won by secular, nonsectarian parties, chiefly the alliance of Prime Minister Nuri al-Maliki. And they represented a defeat for Iran, Moktada al-Sadr and pro-Iran Shiite parties.

“The elections proved the naysayers dead wrong — those who said that the surge might succeed militarily, but fail politically,” says Ken Pollack of the Brookings Institution.

But dangers remain, among which is that Maliki may turn out to be no democrat, but a “strongman” on the model of Egypt’s Hosni Mubarak.

Maliki’s own base political party, Dawa, was modeled on Leninism, one expert told me, and he has routinely resorted to “extra-constitutional” institutions — including his personal paramilitary force — to stifle opposition.

Maliki also tried to rid Iraq’s interior ministry of Sunnis and has ordered the arrest of opponents on trumped up charges.

According to Kagan and Pollack, it’s necessary for U.S. forces to remain as “peacekeepers” — a favored U.S. military role among Democrats — partly to ensure that Maliki doesn’t over-reach.

A U.S. presence also is necessary to ensure that sectarian violence doesn’t break out again, which might happen in the aftermath of a too-hasty withdrawal, and to maintain robust provincial reconstruction teams to help inexperienced, newly elected provincial governments.

Another expert, Stephen Biddle of the Council on Foreign Relations and an original opponent of the war, said during a Washington Post-sponsored blog exchange with Ricks that he, too, favors a slow drawdown.

“U.S. strategic attention is definitely refocusing on Afghanistan,” he said. “There will clearly be a shift of resources. [But] my own preference is for a slower shift than a faster one.

“We need to keep the strategic interests of these two countries in context. Failure in Iraq is still possible and threatens profound U.S. interests in the stability of the Persian Gulf.

“Afghanistan is important, too, but its importance is less direct than sometimes supposed in the U.S. debate and does not necessarily dominate the scale of our continuing interest in Iraq.”

Obama has not declared what his troop withdrawal plan is, but his reaction to the Iraqi elections was that “we are in a position to start putting more responsibility on the Iraqis and that’s good news not only for the troops on the ground, but for the families who are carrying an enormous burden.”

While Odierno is arguing for a slow pace of withdrawal, the high command at the Pentagon, including Joint Chiefs of Staff Chairman Mike Mullen and Army Chief of Staff George Casey reportedly favor speeding it up to give troops longer “dwell time” in the United States before possible deployment in Afghanistan.

The Iraq endgame bears on both Bush’s and Obama’s places in history. A group of historians polled by C-SPAN this month rated Bush seventh from the bottom among the 43 past presidents and second from the bottom in running international affairs.

But Ricks said in a panel discussion at the Center for a New American Security that with the surge, “Bush started being a strategic leader.”

In December 2006, Ricks said, Bush “finally woke up and said, ‘I’m losing the war.’ For the first time, in the next eight weeks, he really became the commander in chief. I think it was his finest moment, those eight weeks.”

Obama, practically every other Democrat and much of the foreign policy establishment was dead against the surge. But “it worked militarily,” Ricks says. He still thinks it failed politically.

Ricks grades the surge campaign with “a solid incomplete.” That has to be Bush’s grade, too. Now, the person who decides Bush’s place in history — and his own — is Barack Obama.