A retired four-star general, who ran a major command, said, "The system is starting to sense the end of the road, and they don’t want to be condemned by history. They want to be able to say, 'We stood up.'"

“What if one hundred thousand Iranian volunteers came across the border?” Nash asked. “If we bomb Iran, they cannot retaliate militarily by air—only on the ground or by sea, and only in Iraq or the Gulf. A military planner cannot discount that possibility, and he cannot make an ideological assumption that the Iranians wouldn’t do it. We’re not talking about victory or defeat—only about what damage Iran could do to our interests.” Nash, now a senior fellow at the Council on Foreign Relations, said, “Their first possible response would be to send forces into Iraq. And, since the Iraqi Army has limited capacity, it means that the coalition forces would have to engage them.”

The Americans serving as advisers to the Iraqi police and military may be at special risk, Nash added, since an American bombing "would be seen not only as an attack on Shiites but as an attack on all Muslims. Throughout the Middle East, it would likely be seen as another example of American imperialism. It would probably cause the war to spread."

In contrast, some conservatives are arguing that America’s position in Iraq would improve if Iran chose to retaliate there, according to a government consultant with close ties to the Pentagon’s civilian leaders, because Iranian interference would divide the Shiites into pro- and anti-Iranian camps, and unify the Kurds and the Sunnis. The Iran hawks in the White House and the State Department, including Elliott Abrams and Michael Doran, both of whom are National Security Council advisers on the Middle East, also have an answer for those who believe that the bombing of Iran would put American soldiers in Iraq at risk, the consultant said. He described the counterargument this way: “Yes, there will be Americans under attack, but they are under attack now.”

In late April, the military leadership, headed by General Pace, achieved a major victory when the White House dropped its insistence that the plan for a bombing campaign include the possible use of a nuclear device to destroy Iran’s uranium-enrichment plant at Natanz, nearly two hundred miles south of Tehran. The huge complex includes large underground facilities built into seventy-five-foot-deep holes in the ground and designed to hold as many as fifty thousand centrifuges. “Bush and Cheney were dead serious about the nuclear planning,” the former senior intelligence official told me. “And Pace stood up to them. Then the world came back: ‘O.K., the nuclear option is politically unacceptable.’ ” At the time, a number of retired officers, including two Army major generals who served in Iraq, Paul Eaton and Charles Swannack, Jr., had begun speaking out against the Administration’s handling of the Iraq war. This period is known to many in the Pentagon as “the April Revolution.”

A former Bush Administration official described a recent meeting between Rumsfeld and four-star generals and admirals at a military commanders’ conference, on a base outside Washington, that, he was told, went badly. The commanders later told General Pace that “they didn’t come here to be lectured by the Defense Secretary. They wanted to tell Rumsfeld what their concerns were.” A few of the officers attended a subsequent meeting between Pace and Rumsfeld, and were unhappy, the former official said, when “Pace did not repeat any of their complaints. There was disappointment about Pace.” The retired four-star general also described the commanders’ conference as “very fractious.” He added, “We’ve got twenty-five hundred dead, people running all over the world doing stupid things, and officers outside the Beltway asking, ‘What the hell is going on?’ ” (my emphasis)

“It’s the bomber mentality,” the Pentagon consultant said. “The Air Force is saying, ‘We’ve got it covered, we can hit all the distributed targets.’ ” The Air Force arsenal includes a cluster bomb that can deploy scores of small bomblets with individual guidance systems to home in on specific targets. The weapons were deployed in Kosovo and during the early stages of the 2003 invasion of Iraq, and the Air Force is claiming that the same techniques can be used with larger bombs, allowing them to be targeted from twenty-five thousand feet against a multitude of widely dispersed targets. “The Chiefs all know that ‘shock and awe’ is dead on arrival,” the Pentagon consultant said. “All except the Air Force.”

“Rumsfeld and Cheney are the pushers on this - they don’t want to repeat the mistake of doing too little,” the government consultant with ties to Pentagon civilians told me. “The lesson they took from Iraq is that there should have been more troops on the ground”—an impossibility in Iran, because of the overextension of American forces in Iraq—“so the air war in Iran will be one of overwhelming force.” (my emphasis)