Iran could have its first atomic bomb within four to six months of the regime's decision to assemble one, according to an assessment last Monday by Amos Yadlin, former IDF Director of Military Intelligence. About a week earlier, Tehran declared that it will now use up to three thousand IR-2M centrifuges, which can enrich uranium at about quadruple the speed of Iran's current enrichment rate. Fred Kagan, Director of the Critical Threats Project at the American Enterprise Institute (AEI), describes the IR-2M installation as "undermin[ing] one of the core assumptions of current U.S. policy": that U.S. intelligence could detect Iran crossing a key threshold and developing weapons-grade nuclear material. The much faster IR-2M centrifuges could enable Iran to produce one weapon's worth of highly-enriched uranium in about a week -  the amount of time that IAEA inspectors might be absent before their next visit.

Why is Iran boldly defying the international community now, in a way that leaves even less time to address its nuclear ambitions? A perfect storm is motivating Iran's sudden sprint to nukes.

The U.S. national security team is in its most ineffective state. Gary Samore, a WMD czar and key member of President Obama's Iran negotiating team, is leaving. John Kerry is in his first days on the job as Secretary of State, and Chuck Hagel - Iran's preferred pick for Secretary of Defense for his anti-Israel and pro-Tehran views - stands a good chance of being confirmed along partisan lines despite his embarrassing display of waffling and incompetence at last week's Senate confirmation hearings.

The rest of the world is preoccupied with the Eurozone economies, the growing spat between Japan and China, the unpredictable North Korean regime, the natural disaster or mishap of the week, and the implosion of Egypt - after the "Arab Spring" turned out to be much less vernal once Egypt's Islamists hijacked it. Oh, and there's Syria and the superpower stalemate that perpetuates the obscenely high daily death toll there. Of course, even if other world powers weren't so preoccupied, they have neither the mettle nor the interest to confront Iran in a way that could actually halt its nuclear program. 

There's still tiny Israel, which can try to address the global threat from a country almost 80 times its size. But here, again, the timing - combined with all of the other circumstances mentioned - conspires to favor Iranian brinksmanship. As logistically complicated and perilous as it would be for Israeli F-15s to attempt a unilateral strike on Iran's protected and dispersed nuclear targets, doing so in winter weather conditions would make the challenge even harder. Israel could still try to neutralize the threat with its submarine and surface-launched ballistic missiles, but because such a strategy - without airstrikes - is even less likely to succeed, the aftermath could be even messier. 

But what choice has the US left one of its closest allies? Is a nation born from the ashes of the Holocaust supposed to sit idly by while terror-sponsoring Iran, which has for decades threatened to destroy Israel, acquires the means to do so?

Of course, nobody wants war: it's better to resolve conflicts peacefully, goes the platitude. So the preferred approach is to resolve the standoff with diplomatic talks. But this has been tried for about a decade without results. As Iran gets closer to the nuclear finish line, it prefers to talk about talks, adding scheduling delays, various preconditions, and venue discussions to buy even more time. And Iran's use of advanced IR-2M centrifuges now leaves even less time to "talk."

Toothless pronouncements of disappointment and condemnation by the US and EU have been as ineffective at stopping Iran's nuclear warpath as they've been at halting Assad's daily massacres. Only a truly credible threat of overwhelming force against Iran can peacefully prevent a potential apocalypse, and only the U.S. can deliver such a threat. The U.S. is also the only power that can produce a peaceful resolution by offering Iran a grand bargain of security guarantees and generous economic incentives. If the Iranian regime is peaceful (or rational), then it should readily accept such a bargain. But if Iran rejects a historic U.S. offer, then its regime clearly has bellicose nuclear intentions that must be stopped by the only power that can do so swiftly and decisively, and without producing a nuclear war that consumes the entire region and leaves many millions dead.

Obama may prefer isolationism but 9/11 provided a painful reminder that pernicious threats can easily find us in our small, interconnected world. The U.S. has failed to lead on Syria, paving the way for the next generation of anti-American jihadists to take root there. Outsourcing the world's greatest security challenge to miniscule Israel is the most reckless form of high-stakes gambling. If the Israelis must act to prevent the prospect of their atomic annihilation by a radical regional theocracy, the impact on the U.S. - from skyrocketing oil prices to regional and security consequences - will make Obama long for the days when he could have confronted the issue at a decidedly lower cost.

Indeed, isolationists must realize that there is no hiding from this problem. Obama's choice is between addressing the Iranian nuclear threat before it explodes into the unthinkable and praying that the U.S. somehow avoids being impacted after Israel is forced to forestall an existential threat as best it can.

Will Obama wait to see if Iran is foolhardy enough to force Israel's hand and start World War III? Or will he lead? Time is short as Armageddon approaches.

Noah Beck is the author of The Last Israelis, a submarine thriller about the Iranian nuclear threat and the doomsday scenario that it could produce.