It significantly inhibits Iran's ability to develop nuclear weapons, in exchange for relief from crippling economic sanctions. Forged over 20 months of intense negotiations among Iran, the U.S., and five other world powers, the Joint Comprehensive Plan of Action is designed to block four possible pathways to the bomb for 10 to 15 years. Iran must relinquish 97 percent of its enriched uranium stockpiles; remove two-thirds of its 20,000 uranium-enriching centrifuges; rebuild its heavy-water reactor so that it cannot produce weapons-grade plutonium; and submit to ongoing, intrusive inspections. These measures are designed to increase Iran's "breakout time" to developing nuclear weapons from the current three months to at least a year. Republicans and Israel strongly opposed the deal, saying it does not guarantee that Iran won't cheat, and may only postpone the Islamic Republic's development of a nuclear weapon. But President Obama insisted that the choice was between a negotiated deal and war. "How can we in good conscience justify war," he asked, "before we've tested a diplomatic agreement?"
It will formally be adopted on Oct. 19, but "implementation day" won't be until the United Nations' International Atomic Energy Agency (IAEA) confirms that Iran has complied with all its obligations. Every stage of Iran's nuclear-fuel supply chain — uranium mines and mills, enrichment plants, centrifuge factories — will be monitored by up to 150 IAEA inspectors, 24/7 video surveillance, and high-tech sensors. If Iran does cheat, said Aaron Stein, a nuclear nonproliferation expert, "the likelihood of getting caught is near 100 percent."