Now that President Obama has been reelected, he faces a number of basic questions about the future of America’s national security strategy. The most immediate of these concerns how the president will address the deep cuts to defense expenditures that will be triggered under last year’s Budget Control Act if congressional Republicans and Democrats can’t reach an agreement on a deficit deal. Answering this question requires a broader sense of the threats we face and what we ought to do about them.

When compared to the height of the Cold War, when the Soviet empire had nuclear weapons trained on virtually every inch of U.S. soil, it is fair to say that the world is a much less dangerous place for Americans, and we shouldn’t forget it. But when compared to the relative peace and security, Islamic terrorism notwithstanding, we’ve enjoyed in the two decades since the Soviet collapse, there is good reason to believe that the threat level is increasing. This is happening at the same time that sluggish economic growth and rising social expenditures are squeezing America’s ability to pay for an enormous military establishment.

Since the 9/11 terror attacks, America’s national security conversation has focused primarily on the threat of mass-casualty terrorism. Hundreds of billions of dollars have been devoted by the public and private sectors to harden domestic targets, with no small success. A fundamental problem, however, is that a free society will always be vulnerable to conventional terrorist attacks, which can be executed by disaffected individuals as well as by highly-trained violent extremists. And while we can harden one set of targets, like airplanes and airports, there will always be softer targets for terrorists to exploit. Moreover, conventional terrorist attacks, as horrifying as they may be, are much less of a threat to public safety in the United States than, say, traffic accidents. John Mueller, a provocative political scientist at Ohio State University, has observed that far fewer Americans died in 2001 from transnational terrorism than from peanut allergies, yet the U.S. government has yet to declare war on peanuts. As awful as it sounds, the best approach to conventional terrorism might be for Americans to allow the intelligence services to do the difficult, painstaking work of containing it while accepting that it will be part of our future in a violent world.

What is unacceptable, however, is nuclear terrorism, which could result in tens of thousands, or even hundreds of thousands, of deaths. One of the ironies of the emerging foreign policy consensus is that while President Obama and his erstwhile presidential rival, Mitt Romney, were both committed to preventing Iran from acquiring a nuclear weapon, both candidates also accepted the idea that U.S. combat troops should leave Afghanistan by 2014. Given the amount of blood and treasure the United States has committed to a seemingly hopeless war in Afghanistan, this consensus is easy to understand. Yet as Stephen Biddle–a political scientist and historian at George Washington University best known for his incisive analyses of Afghanistan and Iraq–has argued, the fall of the U.S.-backed Kabul government to Taliban forces would greatly empower Islamist elements in neighboring Pakistan, where a bona fide civil war is now raging. This matters because Pakistan is a nuclear weapons state in which key figures in the intelligence bureaucracy are known to sympathize with anti-American terrorists. The U.S. presence in Afghanistan can be understood as a hedge against a chaotic collapse of Pakistan that could, in a worst-case scenario, lead to nuclear-armed terrorism. That doesn’t change the fact that the U.S. combat troops will almost certainly leave Afghanistan as planned. But we should not kid ourselves about the risks that this will entail.

Iran is, at least in contrast to Pakistan, relatively stable. A nuclear-armed Iran would be extremely bad news for the United States and its allies in the Gulf for a number of reasons, among them that it may set off a proliferation spiral in which other regional powers seek nuclear weapons of their own; that Iran might become more inclined to engage in military adventurism once it has a nuclear shield against a U.S. counterattack; and that Israel, America’s chief ally in the region, would be extremely vulnerable to an Iranian nuclear strike.