President Obama's first term was marked by the regular and dramatic use of military force: he ramped up troop levels in Afghanistan, increased drone strikes in several countries, bombed Libya and ordered the raid in Pakistan that killed Osama bin Laden.
In his second term, he has used force much more sparingly and his recent foreign policy address at West Point came under considerable criticism for emphasizing what he considers the limits of U.S. military power.
So why such a change?
"My argument would be that what you saw at West Point is the culmination of a trend, and not a real shift in how he thinks about things," says Gary Schmitt, who follows security studies at the American Enterprise Institute.
Obama was more aggressive earlier in his presidency, but he has always been hesitant in engaging in conflict that required an open-ended military commitment, according to a number of analysts.
"What's been consistent is a somewhat conservative view about how the United States can affect changes on the ground and a reluctance to do things that open up the door to needing to do many more things," says Jon Alterman, a global security analyst at the Center for Strategic & International Studies.
Obama inherited the two U.S. wars, in Iraq and Afghanistan, when he took office in 2009. And while he made clear his intention to wind them down, he didn't seem to shy from employing force. He even used his Nobel Peace Prize lecture to make the case for "just war."
According to Double Down, a 2013 book about his re-election campaign by Mark Halperin and John Heilemann, Obama told aides, "I'm really good at killing people," referring to his increased use of drone strikes.
These tough stances helped Obama counter GOP claims that Democrats are weak when it comes to national security.
Thinking About An Exit
But even when he's used force, Obama has had an exit strategy.
Obama withdrew the final U.S. troops from Iraq in December 2011.
He increased the number of troops in Afghanistan, but put a time limit on the deployment. The U.S. combat mission will come to a close by the end of this year. About 10,000 troops will remain to assist the Afghan military and carry out counter-terrrorism operations, but those forces are to be withdrawn by the end of 2016 as Obama's presidency winds down.
In Libya, Obama made clear that American involvement would not extend beyond use of air power, which helped rebels oust dictator Moammar Gadhafi in 2011.
And even the stepped-up use of drones, many commentators have noted, indicated the president wanted a way to hunt and kill terrorists without putting U.S. troops in harm's way.
"It's not unreasonable to say that one reason you're doing drone strikes is you'd rather not be doing boots on the ground," Schmitt says.
Obama has opted against using U.S. military force in Syria or be more confrontational with Russia over its incursion into Ukraine. Both positions have been criticized by Republicans who say he has made the U.S. look weak abroad.
Perceived Limits Of U.S. Power
But Obama believes, as he noted at West Point, that there's only so much that U.S. military might can accomplish in such situations.
"He was always, it seems to me, ambivalent about the utility of military force to solve political problems," says Fredrik Logevall, who directs the Center for International Studies at Cornell University. "He understood that U.S. power, no matter how great in relative terms, is limited."
It's possible that Obama has been chastened, as have so many presidents before him, by the experience of sending young men and women off to die. He told the cadets at West Point that he is "haunted" by the deaths of earlier graduates.
"It does seem to me that he has become more sensitized to the certainty of the horrific costs of American military deaths both the dead, wounded and severely wounded on our side and among innocent civilians in contrast to the highly uncertain payoffs to such involvement," says Ian Lustick, a political scientist at the University of Pennsylvania.
It's often said that second-term presidents focus on foreign policy because they can exercise more control over the ways in which the U.S. responds to the world than they can over Congress and domestic policy.
"Some people would say you're free to do more foreign policy," says AEI's Schmitt. "Maybe his foreign policy is, in fact, to do less."
But it may also be that circumstances, rather than Obama, have shifted during his time in office.
"There is a consistent Obama in this," says Rajan Menon, a political scientist at City College of New York. "What we're seeing is an Obama that tries to accomplish the goals of serving American national security with as few troops on the ground as possible."