President Obama had every right to celebrate the first anniversary of Osama bin Laden’s death with U.S. troops in Kabul. No one can doubt the magnitude of that achievement — under his command.

But everything else about Obama’s Afghan trip had a surreal feel, including his speech to the American public. After 11 years of war, the president had to slip in and out of the country under cover of darkness. Even more disturbing was how little resemblance the speech had to the facts on the ground.

Don’t get me wrong. I understand why any American leader might want to declare victory “within reach” and set a date to bring the troops home — in this case by 2014. Bin Laden is dead and the core al-Qaida leadership has been hard hit by U.S. drone strikes. Recent polls show that only 23 percent of the American public think the United States is doing the right thing by fighting there.

You can criticize Obama for announcing the 2014 date too soon or for front-loading the withdrawal (I’ve done both). However, given the strong opposition to the war and the economic pressures at home, I’d bet a Republican in the White House would also be looking for an Afghan exit.

Yet Obama’s strategy — as laid out in his speech — appears based on a series of unrealistic assumptions that are bound to undermine it. One has to wonder whether he has a Plan B in case the current plan fails.

The essence of Plan A, as the president expressed it: “The tide has turned. We broke the Taliban’s momentum. We’ve built strong Afghan security forces.

“We have begun a transition to Afghan responsibility for security.” By the end of 2014, “we will shift into a support role as Afghans step forward.”

In other words, Key Assumption One is that Afghan forces will be able to keep the country stable and prevent Afghanistan from reverting to a haven for al-Qaida or its allies.

Key Assumption Two: “We are building an enduring partnership” with the Afghans, said Obama, the centerpiece of which is a “Strategic Partnership Agreement” that the president signed in Kabul. This agreement is meant to signify we won’t abandon Afghanistan as we did after the Soviet Union was driven out in 1989, and after the Taliban was defeated in 1991.

The accord sets no figures for future economic aid or funds to support the Afghan security forces, which the Kabul government cannot afford to pay for. Nor does it spell out how many U.S. troops will stay on in the background as trainers and for counterterrorism support. That number will have to be agreed on in a future bilateral security arrangement; if the Iraq experience is any precedent, such an accord might be difficult to reach.

Moreover, once you examine the situation on the ground, the weakness of the president’s key assumptions becomes apparent.

Yes, the Taliban has been driven back in certain provinces, but it’s unclear that Afghan forces can hold the line. In a sign of the challenges they will face, insurgents were able to penetrate a Kabul compound housing Westerners, just after Obama left.

In some key Afghan provinces the Taliban exerts control, especially along the Pakistani border. And Pakistan still refuses to shut down havens for the Taliban inside the country that permit them to regroup.

As for the abilities of Afghan security forces, their unity and coherence remain in serious question. They are dogged by illiteracy, attrition and corruption. Their officer corps is dangerously divided by ethnicity; very few come from the community of southern Pashtuns, where the Taliban problem is greatest.

Moreover, as pointed out by Steve Coll, an expert on Afghanistan and president of the New America Foundation, “The Afghan army and police services require a state to be loyal to — national leadership that they believe in.” They haven’t found it in President Hamid Karzai, or in the corrupt government he leads. Nor is there a clear candidate for 2014 presidential elections who looks likely to unify the country’s ethnic and tribal factions.

Thus, it is very unclear who will be America’s enduring strategic partner in Kabul. What Afghans fear most is that the U.S. troop drawdown will usher in another civil war.

The administration had hoped to head off that prospect by bringing the Taliban into peace talks. Regional diplomacy was supposed to be another key component of the transition, with the goal of dissuading Afghanistan’s neighbors from arming proxies in that country once the Americans leave.

But talks with the Taliban are frozen, in part because of U.S. election-year politics, and regional diplomacy appears stymied. This raises huge questions about whether Obama’s exit strategy can proceed as intended.

“What is Plan B?” Steve Coll asks in a brilliant paper, titled “Can NATO rethink its exit strategy from Afghanistan?” If a majority of the assumptions on which our exit strategy is based are flawed, are we thinking now of alternatives? Or, constrained by politics, will Obama stick to Plan A, even if failure is looming? These are the questions that were left hanging by Obama’s speech.

Trudy Rubin is a columnist for the Philadelphia Inquirer.