President Obama's nuclear posture review (NPR), which defines U.S. policy on nuclear weapons, is less revolutionary than you might think. The NPR is sparking wide debate for narrowing the conditions under which the U.S. would use its substantial nuclear arsenal. Obama's NPR firmly commits, as the New York Times puts it, "not to use nuclear weapons against nonnuclear states that are in compliance with the Nuclear Nonproliferation Treaty, even if they attacked the United States with biological or chemical weapons or launched a crippling cyberattack." This has drawn news reports touting a reduced role for U.S. nukes and cries that we're practically inviting attack.

On the surface, Obama's plan certainly looks like a big deal. For decades, U.S. nuclear policy has been intentionally vague. Refusing to clearly spell out what would provoke an American nuclear retaliation, experts thought, makes the weapons more effective deterrents. Potential enemies would err on the side of not provoking total nuclear annihilation. Obama's plan, by spelling out the conditions of a U.S. nuclear strike, wants to reduce the circumstances in which nukes could be used and minimize the specter of nuclear warfare. But read the NPR carefully and you'll see a gaping loophole ensuring that our nuclear policy goes basically unchanged.

Obama's plan says he will not introduce nuclear weapons to any conflict with a non-nuclear state or with a nuclear state in compliance with the nuclear non-proliferation treaty (NPT). That's virtually all of them. But the exceptions are telling: North Korea, Israel, India, and Pakistan have nuclear weapons in violation of or have not signed the NPT. Iran, if it secures nuclear weapons, will be in violation. So the NPR changes our nuclear policy towards all countries except for the where our nuclear policy most matters: North Korea, Iran, and, to a lesser extent, Pakistan. In those cases, and in the case of any country that develops nukes without international NPT blessing, U.S. policy is fundamentally unchanged. A source within the Washington non-proliferation community tells me some in the field are disappointed by the NPR, which they see as not going far enough. It's not hard to see why.

Of course, Obama's vision of progress has always been as much about changing the way Americans perceive an issue as it is about changing specific policies. It's true that his new nuclear policy is in a lot of ways not new at all. But this NPR carefully frames nuclear weapons not as essential tools of projecting state influence but as dangerous hurdles inappropriate for all but a handful of situations. Though Obama has left a wide exception in his nuclear policy, he's making clear that the cases like Iran and North Korea are just that: exceptions. Vaguely worded, passively threatening nuclear deterrence against non-nuclear threats is no longer the norm. He clearly wants to pave the way for a day when nuclear weapons are used only to deter other nuclear weapons. We're not there yet, but the path is finally visible.