Rarely in wartime is it possible to read over the shoulder of the enemy and discover his most intimate thoughts about the battle. But the United States is claiming just such an intelligence coup with the capture of a letter from Ayman Zawahiri, the cerebral chief strategist of al Qaeda, to his hotheaded field commander in Iraq, Abu Musab Zarqawi.

The July 9 Zawahiri letter was released Tuesday by the office of John Negroponte, the new director of national intelligence. If authentic, the letter takes us inside the tent of al Qaeda's battered but clear-eyed leadership as it plans the next stage of its global jihad.

Al Qaeda in Iraq claims that the letter is a fake, but I would say that, too, if someone had intercepted my battle plans. More troubling is a critique by Juan Cole, one of the leading American experts on Shiite Islam. After carefully reviewing the Arabic text, he argued on his Web site Friday that some of the usage sounds like that of a Shiite or perhaps a Pakistani but not an Egyptian Sunni like Zawahiri. Not so, insist the CIA's Arabic-speaking analysts. "We have the highest confidence in the letter's authenticity," a senior intelligence official reiterated Friday.

At the heart of the letter is an argument that al Qaeda must build a broad political movement in the Muslim world, even as it continues its military campaign to drive America and Israel from the region. Students of 20th-century history will recall a similar shift by the Communist Party in the 1930s, when it moved from a tight, exclusionary strategy to a broader one known as the "Popular Front." Zawahiri's call for mass Muslim politics, which would include those outside his own tight Salafist circle, is plausible because it tracks other recent statements.

"We are in a media battle in a race for the hearts and minds of our umma," Zawahiri advises, referring to Muslim peoples. He chastises his field commander for using brutal tactics that are alienating the masses. "The common folk are wondering," he says, about Zarqawi's slaughter of poor Shiite civilians, his bombings at mosques and his gruesome beheading of hostages, all of which the masses "will never find palatable." In the elaborate politeness of Arabic discourse, Zawahiri is telling his firebrand commander: You are blowing it. We cannot achieve political power by terrifying our fellow Muslims. Here again, the letter, along with other recent indications, reveals that al Qaeda's leadership is unhappy with Zarqawi's cutthroat tactics.

The Zawahiri of the letter is a clever commander. Even on the run, cut off from normal communications, he has a remarkable ability to see the battle space. He takes it for granted that the Americans are pulling out of Iraq and expects some sort of United Nations-sponsored transition. He advises Zarqawi to "fill the void" quickly by establishing a Sunni "emirate" ministate as the Americans leave areas where the insurgents are strong.

The letter also draws a fascinating self-portrait of Zawahiri himself. We sense the vanity of this man who bears an ostentatious prayer mark on his forehead from bowing in prayer so passionately each day. He asks if Zarqawi has seen his appearances on al-Jazeera, read his recent book, listened to his 15 audio statements.

We sense Zawahiri's isolation. He can't see television or read newspapers easily. He complains frequently of being out of touch, and it's clear that some of his couriers have been intercepted, making communication difficult. And he senses that his enemies are closing in. One of his top deputies, Abu Faraj Libbi, was lured into a trap earlier this year, and Zawahiri still seems unclear how it happened. "The real danger comes from the agent Pakistani army," he says -- and he's right. I'm told the Pakistanis have stealthily captured or killed more than 400 of al Qaeda's leaders.

We see, finally, that Zawahiri is being squeezed by Iran. He tells Zarqawi to stop his crazed anti-Shiite attacks because the Iranians are holding more than 100 al Qaeda prisoners, many of them old members of the leadership or part of Osama bin Laden's family. Zarqawi's bloodthirsty assault on the Shiites, he says, "compels the Iranians to take countermeasures." If the letter is an Iranian forgery, which is one of the possibilities Cole suggests, it's a diabolically astute one.

Reading the Zawahiri letter, you sense that the field of battle is shifting. Al Qaeda is waging a political war for Muslim hearts and minds as it seeks to build a global caliphate. America shouldn't make the same mistake for which Zawahiri is upbraiding his Iraq commander -- fighting in the Iraq theater in ways that make it harder to win the larger war.