Air Force One touched down late at night local time at Bagram Air Field, the main U.S. base here.

Media traveling with Obama on the 13-hour flight had to agree to keep it secret until Obama had safely finished a helicopter flight to the nation’s capital, Kabul, where Taliban insurgents still launch lethal attacks.

Obama is joining Afghan President Hamid Karzai to sign the agreement that will broadly govern the U.S. role in Afghanistan after the American combat mission stops at the end of 2014 — 13 years after it began.

Obama will also give a speech designed to reach Americans in the U.S. dinnertime hour of 7:30 p.m. EDT. It will be 4 a.m. here when Obama speaks.

His war address will come exactly one year after special forces, on his order, began the raid that led to the killing of bin Laden in Pakistan.

Since then, ties between the United States and Afghanistan have been tested anew by the burning of Muslim holy books at a U.S. base and the massacre of 17 civilians, including children, allegedly by an American soldier.

Obama’s overarching message will be that the war is ending on his watch but the U.S. commitment to its ally is not.

Politics, too, set the tone for what the White House hoped would be a positive message and image for Obama: the commander in chief setting a framework to end the war while reassuring Afghanistan, on its soil, it will not be abandoned.

At home, Obama’s Republican opponent, Mitt Romney, has retorted to the Obama campaign’s suggestion that Romney might not have gone after bin Laden as Obama did.

“Even Jimmy Carter would have given that order,” Romney said of the Democratic president ousted after one term.

Obama has tried to portray inconsistency in Romney’s position on the merits of targeting bin Laden. Without mentioning Romney by name, Obama has said he has been consistent and if others have not, “let them explain it.”

Obama aides said the anniversary of bin Laden’s killing is not a focus of the trip. But they do not mind that Obama’s mission will serve as a reminder, six months before Election Day.

More than 1,800 U.S. forces have been killed and 15,700 more have been wounded in Afghanistan.

The wars in Afghanistan and Iraq combined have cost almost $1.3 trillion. And public support for keeping troops in Afghanistan seems lower than ever.

Obama has gone twice before to Afghanistan as president, most recently in December 2010, and once to Iraq in 2009. All such trips, no matter how carefully planned, carry the weight and the risks of considerable security challenges. Just last month, the Taliban began near-simultaneous assaults on embassies, government buildings and NATO bases in Kabul.

Still, it would have been unusual for Obama to sign the “strategic partnership” agreement without Karzai at his side.

The deal is essential for locking in America’s commitment and Afghan’s sovereignty when the post-war period comes. Negotiations have dragged as Afghan officials have demanded specific assurances, financial and otherwise.

Both sides have scrambled to get a deal before the NATO conference in Chicago later this month. Negotiators seemed to clear the way for Obama and Karzai by finding agreement over the conduct of night raids and authority over detainees.

The president was to travel back from Kabul to the Bagram base to spend some time with troops.

He was then to give his speech in a straight-to-camera delivery reminiscent of an Oval Office address, before flying back to the U.S. He is expected back in Washington on Wednesday afternoon.

The United States has 88,000 troops in Afghanistan. An additional 40,000 in coalition forces remain from other nations.

Obama has already declared that NATO forces will hand over the lead combat role to Afghanistan in 2013 as the U.S. and its allies work to get out by the end of 2014.

One important unsettled issue, however, is how many U.S. troops may remain after that.

U.S. officials are eying a residual force of perhaps 20,000, many in support roles for the Afghan armed forces, and some U.S. special forces for counterterror missions. The size and scope of that U.S. force — if one can be agreed upon on at all, given the public moods and political factors in both nations — will probably have to be worked out later in a separate agreement.

Support for keeping American troops in Afghanistan is dropping all along the political spectrum, a new Pew Research poll says. And just 38 percent of people say the military effort is going well, down from 51 percent only a month ago.

Overall, polling shows, Obama gets favorable marks compared to Romney in handling terrorism, and the president’s public approval for his handling of the Afghan war has hovered around 50 percent of late.

The trip allows Obama to hold forth as commander in chief in the same week he plans to launch his official campaign travel with rallies in Virginia and Ohio.

“We’ve spent the last three-and-a-half years cleaning up after other folks’ messes,” Obama said at a fundraiser last weekend. “The war in Iraq is over. We’re transitioning in Afghanistan. Al-Qaida is on the ropes. We’ve done what we said we’d do.”

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AP National Security Writer Anne Gearan, Deputy Director of Polling Jennifer Agiesta and News Survey Specialist Dennis Junius contributed to this story.

The broader goal for Obama, whether through campaign web videos or the trappings of the White House, is not to just to remind voters of an enormous victory on his watch. It is to maximize a political narrative that he has the courage to make tough calls that his opponent might not.

“Does anybody doubt that had the mission failed, it would have written the beginning of the end of the president’s first term?” Vice President Joe Biden says in laying out Obama’s foreign policy campaign message. “We know what President Obama did. We can’t say for certain what Governor Romney would have done.”

The strategy underscores the fact that the Obama who ordered the raid as commander in chief is now seeking a second term as president. The risk is the political blowback that can come if he is seen as crossing a line into politicizing national security.

“Sad,” said a Romney spokeswoman. “Shameless,” said 2008 Obama election foe John McCain.

Biden even combined the killing of the al-Qaida leader and Obama’s support for a failing auto industry into what he called a re-election bumper sticker message.

“It’s pretty simple: Osama bin Laden is dead and General Motors is alive,” the vice president said in a speech on Thursday.

Obama’s campaign followed that Friday with a new web video questioning whether Romney would have taken the same path Obama did. If features a quote from a 2007 Romney interview in which he said it was not worth “moving heaven and earth spending billions of dollars just trying to catch one person.”

That prompted Obama’s 2008 opponent, Arizona’s McCain, to issue a scathing statement in which he accused Obama of playing politics with the bin Laden killing and “diminishing the memory of September 11th.”

“This is the same president who said, after bin Laden was dead, that we shouldn’t ‘spike the ball’ after the touchdown,” he said. “And now Barack Obama is not only trying to score political points by invoking Osama bin Laden, he is doing a shameless end-zone dance to help himself get re-elected.”

The president’s initial words on the bin Laden mission — a raid for which he received wide praise, including from Romney — were ones of sober thanks. Addressing the nation late that night of May 1, 2011, in Washington, Obama said: “Tonight, let us think back to the sense of unity that prevailed on 9/11.”

So much for that, the Romney campaign said Friday.

“It’s now sad to see the Obama campaign seek to use an event that unified our country to once again divide us, in order to distract voters’ attention from the failures of his administration,” Romney spokeswoman Andrea Saul said.

Obama campaign spokesman Ben LaBolt declined comment for this story, saying Biden’s speech and the new campaign video speak for themselves.

White House spokesman Jay Carney said the bin Laden raid is a part of Obama’s foreign policy story, and “I think the way that we’ve handled it represents exactly the balance you need to strike.”

President George W. Bush, when seeking re-election in 2004, faced criticism that he was politicizing the memory of the Sept. 11, 2001, attacks, including with a video at the Republican National Convention that credited him with “the heart of a president.”

Steve Schmidt, a spokesman and strategist for that Bush campaign, said the bin Laden killing is fair game as a campaign message for Obama.

“It was a courageous political decision to launch the raid where bin Laden was killed. The stakes were enormous,” Schmidt said. “Had it gone south, there would have been tremendous political ramifications for the president. It’s a real event that happened on his watch, by his command.”

In perspective, Schmidt added, the issue won’t be a determining factor in an election to be driven by the economy.

Bin Laden was killed in Pakistan by U.S. Navy SEALs. The terror leader was living in a compound in one of Islamabad’s suburbs, having evaded capture for nearly 10 years.

The episode is featured prominently in a longer Obama campaign video, narrated by actor Tom Hanks, as an example of decisive leadership.

Obama sent in the U.S. forces with no assurance that bin Laden was at the site, leading to a heart-pounding scene in the Situation Room, captured in one of the most famous photos of Obama’s presidency.

From that room, Obama will relive the moment in prime time. The White House granted NBC News’ Brian Williams access to the Situation Room, and interviews with Obama and top members of his security team, for a special that has been taped and will air on Wednesday.

It is unclear if the room has been used before as the setting for such an interview. NBC News called it a first for network television. White House national security spokesman Tommy Vietor said the room itself is only classified if the topic being discussed is, and that reporters have been inside the room before.

Said Schmidt: “It’s part of the advantage of being an incumbent president.”