WASHINGTON?President Barack Obama rushed to the Oval Office when word arrived one night that al-Qaida militants in Yemen had been located and that the military wanted to support an attack by Yemeni forces. After a quick discussion, his counterterrorism adviser, John O. Brennan, told him the window to strike was closing.

?I?ve got two minutes here,? Brennan said.

?OK,? Obama said. ?Go with this.?

Brennan raced to the Situation Room to transmit the order.

While Obama took three sometimes maddening months to decide to send more forces to Afghanistan, other decisions as commander in chief have come with dizzying speed, far less study and little public attention.

He is the first American president in four decades with a shooting war already raging the day he took office?two, in fact, plus subsidiaries?and his education as a commander in chief with no experience in uniform has been a steep learning curve.

He has learned how to salute. He has surfed the Internet at night to look into the toll on troops. He has faced young soldiers who had been maimed after carrying out his orders. And he is trying to manage a tense relationship with the military.

Biggest choices

Along the way, he has confronted some of the biggest choices a president can make, often deferring to military advisers yet trying to shape the decisions with his own judgment?too much at times for the Pentagon, too little in the view of his liberal base.
His evolution from antiwar candidate to leader of the world?s most powerful military will reach a milestone on Tuesday when Obama delivers an Oval Office address to formally end the combat mission in Iraq while defending his troop buildup in Afghanistan.
A year and a half into his presidency, Obama appears to be a reluctant warrior. Even as he draws down troops in Iraq, he has been abundantly willing to use force to advance America?s interest, tripling forces in Afghanistan, authorizing secret operations in Yemen and Somalia, and escalating drone strikes in Pakistan.

But advisers said Obama did not see himself as a war president in the way his predecessor did. His speech on Tuesday will be notable in part because he will talk in public about the wars only sporadically, determined not to let them define his presidency.

While George W. Bush saw the conflicts in Iraq and Afghanistan as his central mission and opportunities to transform critical regions, Obama sees them as ?problems that need managing,? as one adviser put it, while he pursues his own mission of transforming the United States.

Uneasy balance

The result, according to interviews with three dozen administration officials, military leaders and national security experts, is an uneasy balance between a president wary of endless commitment and a military worried that he is not fully invested in the cause.

?He?s got a very full plate of very big issues, and I think he does not want to create the impression that he?s so preoccupied with these two wars that he?s not addressing the domestic issues that are uppermost in people?s minds,? Defense Secretary Robert M. Gates said in an interview.

Sen. Jack Reed, who sometimes advises Obama, said the president was grappling with harsh reality. ?He came into office with a very sound strategic vision,? Reed said, ?and what has happened in the intervening months is, as with every president, he is beginning to understand how difficult it is to translate a strategic vision into operational reality.?

Running for president of a country at war, Obama had plenty to learn, even basics like military ceremonies and titles. His campaign recruited retired generals to advise him. But it still took time to adjust when he became president. The first time he walked into a room of generals, an aide recalled, he was surprised when they stood. ?Come on, guys, you don?t have to do that,? he said, according to the aide.

Most important tutor

Perhaps Obama?s most important tutor has been Gates, the defense secretary appointed by Bush and the first kept on by a president of another party. They are an unlikely pair?a 49-year-old Harvard-trained lawyer turned community activist and a 66-year-old veteran of Cold War spy intrigues and Republican administrations. But they have bonded through weekly lunches and shared challenges.

Obama has relied on Gates as his ambassador to the military and deferred to him repeatedly.

Even on his signature campaign promise to pull out of Iraq, Obama compromised in the early days of his tenure to accommodate military concerns. Instead of the 16-month withdrawal of combat forces he promised, he accepted a 19-month timetable, and he agreed to leave behind 50,000 troops for now rather than a smaller force.

But as he grows in the job, Obama shows more willingness to set aside Gates? advice.

When Gen. Stanley A. McChrystal got into trouble in June for comments by him and his staff in Rolling Stone magazine, Gates favored reprimanding the commander.

Obama decided instead to oust McChrystal and replace him with Gen. David H. Petraeus, who led the troop increase in Iraq. New York Times News Service