That was when denizens of the Oval Office had one powerful attribute: ambition. And that’s exactly what President Barack Obama is lacking today: a desire to shape world events to America’s liking, and a willingness to take big risks to make that happen.

No wonder he is making little progress on the enormous foreign policy and national security challenges facing the United States. The less ambition an administration has, the harder achieving anything becomes.

While trying to tackle hard problems can make them more complicated, not tackling at least some of them in a serious way increases the likelihood that they will get worse. Success will come, if at all, against long odds. Without trying, failure is guaranteed.

For the president, significant diplomatic accomplishments seem nowhere in sight. Instead, the terrain looks barren or smoldering with problems from hell in Syria, Egypt and elsewhere, a Putinized Russia, and a China that is asserting territorial claims in troubling ways.

This unwelcome landscape helps explain the modesty of the Obama administration’s foreign policy and national security aims. If one is unlikely to make serious progress on very hard problems, and if Sisyphean efforts might well complicate matters further, why try?

One good reason is that, without ambition, firefighting becomes the default position, as was evident during Hillary Clinton’s tenure as secretary of state. She either didn’t seek or wasn’t given the lead on the Middle East, China, Russia, and nonproliferation portfolios. It’s perfectly acceptable for the White House to hold on to every one of them, but what’s the point of doing so in order to pursue modest initiatives?

Administrations that make their mark on the world have great ambition at rare junctures of dramatic change and opportunity. It’s the Obama administration’s lot to operate in a changing international environment that seems devoid of opportunity.

Some problems from hell might burn themselves out and others must be handled with care, especially after expending so much blood and treasure in Iraq and Afghanistan. Wars that are poorly conceived, planned and executed are unlikely to end well, and have a properly chastening effect.

The George W. Bush administration’s use of hard power and the Obama administration’s use of soft power have not increased U.S. persuasiveness abroad. So, what is an administration to do when no hard and consequential problem seems ripe for diplomatic accomplishment?

Diplomatic risk-taking is a high wire act, with only four potential wire-walkers: the president, vice president, the secretary of state, and the national security advisor.

Secretary of State John Kerry, unlike his predecessor, has been cleared by the White House to walk the high wire. He has decided that a renewed effort to seek an Israeli-Palestinian settlement is worth the effort and that failure to try is likely to have dire consequences. His ambitious and draining efforts stand in stark contrast to the administration’s apparent lack of ambition on other hard national security problems.

The Obama administration can’t be blamed for its lack of ambition in dealing with Vladimir Putin, whose choices continue to mortgage Russia’s future.

Opportunities for a strategic opening with Beijing offer more hope. The most promising avenue of increasing strategic cooperation with China lies in space, rather than on nuclear issues. A collaborative space initiative and a code of conduct setting or strengthening norms for responsible space-faring nations could have strategic import. But so far, there are no takers for high-wire walking between Washington and Beijing.

Pakistan has a new prime minister, Nawaz Sharif, who wants to increase trade and otherwise normalize relations with India. He and Indian Prime Minister Manmohan Singh have appointed trusted individuals for back-channel talks, eliciting the usual qualms from the usual quarters. Spoilers are at work, creating incidents along disputed borders. Washington has no place getting in front of this process, but does not even appear to be in the rear-view mirror, prodding or offering incentives from behind the scenes.

North Korea has a new, young leader who has started out by making poor decisions. Washington has chosen not to see whether he might embark on a different course. Instead of seeking direct dealings with Kim Jong-un, the Obama administration seems content with multilateral approaches that offer little prospect for gain.

The most glaring absence of ambition at present appears to be in the run-up to nuclear negotiations with a newly elected Iranian President Hassan Rouhani. A window of opportunity for significant deal making may well be narrow, but it is now open. This window will shut quickly if the Obama administration approaches the renewal of talks with an abundance of timidity, as if the next move depends on how Tehran reacts to its last cautious gambit.

Sanctions, no matter how harsh, are a means to an end. Like sanctions, the threat of military strikes against Iranian nuclear facilities will not help produce a satisfactory diplomatic settlement unless an ambitious U.S. initiative is forthcoming. Many seasoned diplomats, including high-ranking nonproliferation officials who have recently departed from the Obama administration, have called for a more ambitious negotiating approach. They are not known for throwing caution to the wind, and have good reason to be skeptical of success. And yet, they still advise an ambitious offer at this juncture. If the effort is made, success may well remain elusive. If an ambitious proposal is not offered, failure seems assured, with consequences to follow.

What ever happened to the audacity of hope?

Michael Krepon is co-founder of the Stimson Center, a nonprofit and nonpartisan international security think tank, and the author of “Better Safe than Sorry: The Ironies of Living with the Bomb.”

CORRECTION: A previous version of this article cited Iran instead of Iraq in the ninth paragraph.