Israeli Prime Minister Benjamin Netanyahu has been campaigning for an unambiguous red line to stop Iran's nuclear advance. In an infelicitous foray into American politics last month, he took to the Sunday morning television shows to insist that Barack Obama act to stop Iran, saying, "You have to place that red line before them now." Smarting from the Obama administration's refusals, he challenged the U.S. president with the zinger: "Those in the international community who refuse to put red lines before Iran don't have a moral right to place a red light before Israel." Then, at the U.N. General Assembly meeting, he held up a cartoon of a bomb and with a marker drew a red line, declaring that Iran could not be allowed to produce a stockpile of 20 percent enriched uranium sufficient (after further enrichment) for its first nuclear bomb. On the current trajectory, as laid out in the public reports of the International Atomic Energy Agency, Iran will reach that point in about six months.

As he addresses Iran's nuclear challenge, the prime minister's frustration stems from his knowledge that Israel and the United States have been complicit in a process of drawing red lines they say Iran will never be allowed to cross, watching Iran cross those lines, and then retreating to declare the next obstacle on the path to a bomb to be the real red line.

Addressing the U.S. Congress in 1996, Netanyahu, then serving his first term as prime minister, argued that Iran's acquisition of a nuclear bomb would have "catastrophic consequences, not only for my country, and not only for the Middle East, but for all mankind." He warned that the deadline for preventing that outcome was "getting extremely close." Israel declared Iran's possession of a civilian nuclear power plant "unacceptable" until it became operational, when the Israeli Foreign Ministry declared this "totally unacceptable."

Nor was this the last time Israeli politicians and officials have announced a point of no return, only to move the goal posts later. For Prime Minister Ariel Sharon in 2004, it was development of a "technical capability" for operating an enrichment facility. As Iran approached that capability, Defense Minister Shaul Mofaz described the tipping point not as the capability, but as the "enrichment of uranium" itself. After Iran began enriching uranium, Prime Minister Ehud Olmert drew a new line in 2006 as enrichment "beyond a limited number of cascades."

The pattern is clear: As Iran has crossed each red line, Israel has retreated to the next and, in effect, hit the repeat button. From conversion of uranium, to production of low-enriched uranium (less than 5 percent) that can be used as fuel for civilian power plants, to a stockpile of low-enriched uranium sufficient (after further enrichment) to make one nuclear bomb, to a stockpile sufficient for half a dozen bombs, to enrichment beyond 5 percent to 20 percent medium-enriched uranium, to operation of centrifuges enriching to 20 percent at the deep underground facility at Fordow, to achievement of a undefined "nuclear weapons capability," Israel's warnings have grown louder, but with no more effect.