Ever since the Revolution 230 years ago, Americans have insisted that their soldiers scrupulously obey the orders of properly constituted political leaders, elected and appointed, placed over them.

Rarely has that principle been challenged. In the Civil War, President Abraham Lincoln dismissed Gen. George McClellan for failing to carry out orders. In the Korean War, President Harry Truman fired Gen. Douglas MacArthur for insubordination.

Even in the recent eruption of criticism of Secretary of Defense Donald Rumsfeld by a half-dozen retired generals, no one has disputed his authority. Instead, the generals have questioned his competence, judgment and conduct of the war in Iraq. Several have called on him to resign.

Those allegations have triggered an argument that has swirled into partisan politics, debate over Iraq, Rumsfeld's abrasive style and military transformation. President Bush has defended his defense secretary, and Rumsfeld has attributed the criticism to changes he has demanded in the armed forces.

Amid this turbulence, the key point has almost been lost: When and under what circumstances may a military officer disagree with his civilian superiors? Indeed, are there times when an officer is morally obliged to dissent?

Accepted ethics say a serving officer may speak up within the councils of government and, more, is obligated to offer his professional assessment on military matters. Bernard Trainor, retired Marine lieutenant general, and Michael Gordon, military correspondent for The New York Times, report in their book, "Cobra II," that plans for invading Iraq were intensely debated within the Pentagon.

When an officer testifies before a congressional committee, he is obliged by law and protocol to render his best judgment. Gen. Eric Shinseki, then chief of staff of the Army, was asked in 2003 how many soldiers would be required to occupy Iraq, an issue of much disagreement inside the Pentagon.

Shinseki said "several hundred thousand soldiers" would be needed to "maintain a safe and secure environment, to ensure that people are fed, that water is distributed, (and to fulfill) all the normal responsibilities that go along with administering a situation like this."

For that, he was publicly censured by Rumsfeld, who contended it would take far fewer soldiers. The former chairman of the joint chiefs of staff, Gen. Richard Myers, said Shinseki was required to give an honest answer, saying: "There were some mistakes made by, I think, some of the senior civilian leadership in taking Gen. Shinseki on about that comment."

After a decision is taken with which the officer does not agree, he can either salute and execute or he can advise his superiors that he cannot abide by the decision. He then falls on his sword by resigning or retiring.

The quarrel today is whether an officer should speak up after he has retired. Honorable soldiers disagree on the propriety of doing so.

One school holds that retired officers have an obligation to challenge political leaders if they think American men and women are dying needlessly in the sands of Iraq. Retired officers, like other citizens, are also guaranteed freedom of speech under the Constitution.

Gen. Anthony Zinni, a retired Marine, called for Rumsfeld's resignation on a TV news program in early April. He also pointed at officers who had failed to speak up. "There were appropriate ways within the system that you can speak out — at congressional hearings and otherwise," he said. "I think they have to be held accountable."

The other school says retired officers should keep quiet so as not to damage the morale of troops in battle nor aid an enemy who might see dissent as weakness. Moreover, retired officers may not be so well informed on the current situation and could, by public criticism, complicate the efforts of those responsible.

Shinseki, who argued vigorously with Rumsfeld privately while he was chief of staff, has refused to be drawn into public debate over his disagreements.

In a rare comment, he told Newsweek succinctly: "Not my style."

Either way, soldiers have sometimes agonized over their decisions. Gen. Harold K. Johnson, an Army chief of staff during the Vietnam war, considered resigning to protest the way President Lyndon Johnson ran the war but decided not to, and regretted his choice.

Military historian Lewis Sorley reports that the general told a friend: "I made the typical mistake of believing I could do more for the country and the Army if I stayed in than if I got out. I am now going to my grave with that lapse in moral courage on my back."

Richard Halloran is a Honolulu-based journalist and former New York Times correspondent in Asia.