EVENTS ARE CONVERGING TO ELEVATE the nuclear crisis with Iran into the central crisis of the Bush presidency. War presidents are graded not by circumstances they inherit, including those that lead to war. They are judged by how they react to those circumstances.

Franklin Roosevelt as a war president is defined not by the attack on Pearl Harbor, but by the radical war aim he laid out against Japan and Germany in the wake of Pearl Harbor--unconditional surrender--and by his relentless and successful pursuit of that war aim until the day he died.

When Lyndon Johnson became president in November 1963, he inherited a chaotic situation in South Vietnam due to an ill-advised military coup against the civilian-led Saigon government countenanced by his predecessor, John F. Kennedy. As vice president, LBJ had fought to prevent the anti-Diem coup, which proved to be a ghastly mistake. Yet Johnson as a war president receives a failing grade for one reason only: When he left office in January 1969 the United States was in a far weaker geopolitical position, in Vietnam and globally, than it had been when Johnson took office.

In the same way, long after the present wartime president leaves office, his success or failure will be judged not by the enemy attacks of 9/11 but by how he responded to those attacks--and by whether his responses prove right or wrong.

In response to 9/11, Bush and his administration put down clear markers and bright lines. The days of treating terrorism as a criminal activity, to be solved primarily by the work of policemen, prosecutors, judges, and juries, were over. The president served notice that foreign governments providing safe haven for terrorist enemies of the United States would be treated as if those governments were mounting terrorist operations themselves--that is, as enemies of the United States in a world war. And he announced that rogue states would not be allowed to acquire weapons of mass destruction.

To achieve these war aims, Bush proclaimed two new doctrines. The new military doctrine, a marked departure from the Cold War doctrine of deterrence, was that of preemption: We would no longer wait for military mobilizations or attacks before striking against a growing terrorist threat. Preemption comprised a series of military options up to and including invasion, occupation, and regime change.

The new geopolitical doctrine was the promotion of democracy as a central U.S. policy goal around the world but with particular focus on the Arab and Islamic cultures. Without political reform in the Islamic world, Bush argued, eliminating one set of terrorists would achieve no more than a respite before terrorism's next wave.

By the time of the January 2002 State of the Union speech that singled out an "axis of evil"--Iraq, Iran, and North Korea--as the most dangerous of the world's surviving rogue states, Bush had successfully defined his response to 9/11. He had also laid out a coherent U.S. military and political strategy to deal with the protracted world war he believed us to be in. You could disagree with the strategy, and many did. But no one could deny that such a strategy had been laid out.

In the years since 9/11, the Bush war strategy has yielded some undeniable successes: the turning of Pakistan from a fomenter of terrorism and of nuclear proliferation into a semicollaborator of the United States; the ousting of the Taliban government and its al Qaeda mentors in Afghanistan; and the renunciation by Libya of its nuclear program, to name three. Claims can be made as well for the Syrian withdrawal from Lebanon followed by free elections and for the advance of democratic reforms in a number of other Islamic countries.

Beginning with the March 2003 invasion, the war in Iraq has taken center stage as the toughest, best-defined test of the Bush war strategies: in a nutshell, military preemption and regime change, followed by democratic reform in the wake of terrorist challenges from Sunni revanchists and Islamist terrorists swearing allegiance to al Qaeda. Iraq has tested every element of the Bush war strategy. Until fairly recently, it seemed plausible that the success or failure of Bush's global strategies, and thus of the Bush presidency itself, would hinge on U.S. success or failure in Iraq.

With the election of Mahmoud Ahmadinejad as president of Iran last June, this began to change. There may or may not be elements in the Iranian government willing to accommodate the emerging Shiite-majority government in Iraq. There may even be factions in Iran that would hesitate before providing a direct challenge to Bush's preemption doctrine. If such factions exist, however, they are irrelevant today. Ahmadinejad, for whatever reasons, appears determined to force Bush to live up to his post-9/11 strategy or tacitly admit that he has abandoned it in the face of difficulties in Iraq.

One by one, Iran's radical president is removing the pretexts for U.S. inaction or delay. Could we live with a nuclear Iran? Not one led by a man who says the Jewish Holocaust never happened and muses about the possibility of correcting that Nazi failure by dropping a nuclear bomb on Israel. Is there a way to take advantage of the fact that the Shiite wing of Islamism has not taken part, so far, in a shooting war with the United States or its allies? Not with an Iranian president who convenes a terror summit in Damascus with Bashar Assad, the all-but-proven murderer of the former premier of Lebanon, and with Hamas, the avatar of Sunni terrorism in the Palestinian territories. Given these events, it would no longer be shocking to see Ahmadinejad at a summit with Abu Musab al-Zarqawi, the head of al Qaeda in Iraq and an advocate of the mass murder of Shiites as a tactic in the war against U.S. forces and the Shiite-led Iraqi government.

Reports out of Iran suggest Ahmadinejad may see himself as a central actor in an Islamic apocalypse. A man with this mindset might see provoking the United States as forwarding the end game of Allah. And he might not fear provoking Israel into an attack on Iran's nuclear facilities that could trigger convulsions throughout the Middle East and beyond.

Much depends on how far Iran is from putting together its first nuclear warhead. Some reports, particularly those traced to Israeli intelligence, point to the very near future. Even if the ominous date turns out to be much further away, Ahmadinejad shows little sign of pausing for breath. Indeed, the Hamas sweep of the Palestinian parliamentary elections is no doubt being seen in Tehran as a vindication of Ahmadinejad's Damascus terror summit days earlier.

If the Bush administration is developing a military option to deal with Iran's acquisition of nuclear weapons--a form of preemption--it is doing so very quietly. On the pure military level, this is, of course, appropriate. If you had to pick one flaw in the superbly organized U.S. invasion of Iraq, as Jed Babbin recently pointed out, it would be the lack of an element of surprise.

But what is starting to become clear is that Ahmadinejad's seemingly reckless challenge will extract, and is meant to extract, a cost in U.S. standing among our friends and allies, in Iraq and across the globe. A war president who can be portrayed as having given up on the core of his own war strategy will be seen as a leader considerably less capable of deterring our terrorist enemies, wherever they are and whatever it is they are plotting.

Jeffrey Bell is a principal of Capital City Partners, a Washington consulting firm.

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