On Sept. 17, Israeli Prime Minister Benjamin Netanyahu told the United Nations that the world must draw a clear "red line" around the Iranian nuclear weapons program, and tell the Tehran regime that if that line is crossed, war will ensue. He said the red line should be drawn right now, so that there is no room for ambiguity, and he added that "red lines don't lead to war, red lines prevent war."
Serious strategic thinkers have long argued that it's dangerous to encourage an enemy to believe he can take provocative action without serious consequences. In the 20th century, several ambitious leaders marched into war at least in part because they believed their potential enemies would not respond. Adolf Hitler was never told to stop -- or else -- and didn't, until the West had to fight a world war. North Korea invaded the South in part because the United States gave no clear indication it would enter the fight. Saddam Hussein invaded Kuwait in 1990 in part because the American ambassador to Baghdad told him that the United States had no opinion on "Arab-Arab conflicts, like your border dispute with Kuwait."
And, of course, there is the celebrated phrase from the Roman military strategist Publius Flavius Vegetus: "If you want peace, prepare for war." Mr. Netanyahu was in good company when he called for clarity, and he was on solid ground when he said that red lines can avoid wars.
It sometimes seems as if President Obama agrees with Mr. Netanyahu's assessment. Like Mr. Netanyahu, Mr. Obama has said that we cannot permit Iran to become a nuclear power, and he has warned, albeit not in so many words, that the United States would take any and all measures, including going to war, to prevent Iran from obtaining atomic bombs. To be sure, Mr. Obama has not said the United States would use its military arsenal, but he and his colleagues have often said that "the military option is on the table."
However, there is a vital disagreement between the Israeli and American governments over the location of the "red line." The Israelis, who fear they would be the first target of an Iranian nuclear arsenal, have said that they would have to take action once Iran obtained the capacity for atomic weapons, while the Americans insist that the red line would only be crossed when Iran actually obtained a bomb.
Moreover, this disagreement comes wrapped in the fog of "intelligence assessments." Given the rash of recent intelligence failures, how could the two leaders have confidence they would know precisely when Iran had either the capacity for building a bomb or the bomb itself? Vice President Joseph R. Biden Jr. blithely told vice-presidential candidate Paul Ryan that we would certainly know it, and that there would be plenty of time to take appropriate action, but the history of American knowledge of foreign nuclear programs does not inspire confidence. We have often been surprised when countries from the Soviet Union to Pakistan suddenly tested their bombs.
Thus, even if the Israelis had total confidence in the reliability of the United States, they would have good reasons to prepare to attack the Iranian nuclear program. They don't have the luxury of waiting for an Iranian nuclear test -- which they fear might be conducted on Israeli soil, after all -- before taking action. They can't be at all confident that the Americans will share their assessment of the state of affairs in Iran.
Finally, the Israelis are not confident that the Americans will join them, even if there were clear evidence that Iran had nuclear weapons. We need look no further than recent events in Libya to understand why. If Washington did not act to protect American diplomats and security forces in Benghazi, despite repeated pleas for greater security from our personnel on the ground there, how can Israeli leaders expect this administration to help defend them?
On the other side of the line, why should Supreme Leader Ali Khamenei and his henchmen in Tehran fear a devastating American response to an Iranian attack against Israel, when, for decades, we have failed to respond to repeated Iranian assaults against Americans? In the past few days, an American court heard a would-be assassin confess to planning carnage -- hand-in-glove with the Iranian regime -- in Washington. To date, our response has been limited to turning the entire matter over to a judge.
I have long opposed military action against the Iranian regime. I believe we should instead support democratic revolution. However, our failure to work for regime change in Iran and our refusal to endorse Mr. Netanyahu's call for a bright "red line" around the mullahs' nuclear weapons program, makes war more likely, as similar dithering and ambiguity have so often in the past.
Michael Ledeen is a freedom scholar with the Foundation for Defense of Democracies.