[Geoffrey Perret has written 13 books of history and biography, including “Ulysses S. Grant,” “Eisenhower” and “Lincoln’s War.” His most recent book is “Commander in Chief: How Truman, Johnson, and Bush Turned a Presidential Power into a Threat to America’s Future.”]

What the military needs now is a number of senior generals and admirals who are willing and able to debate the president and the secretary of defense — and a president and secretary of defense who are big enough to accept disagreement and even learn from it. This would re-establish a tradition that gave the armed services their greatest commanders and America a history of military victory.

Ever since George Washington was president, military officers and politicans have had lively disputes. Probably the most melodramatic came in 1933, when Douglas MacArthur protested deep cuts proposed for the Army’s budget. When Franklin Roosevelt refused to relent, MacArthur’s heated response was, “Mr. President when we lose the next war and an American boy lying in the mud with an enemy bayonet through his belly and an enemy foot on his throat, spits out his last curse, I want the name on his lips to be Roosevelt, not MacArthur.” He concluded by saying he was resigning (though he didn’t really). Roosevelt canceled most of the proposed cuts.

The break in tradition began with Harry S. Truman’s accession to the presidency in April of 1945. As a young man, Truman had applied to both West Point and Annapolis, but had been rejected for having poor eyesight. He came to the presidency with nothing but envy-colored contempt for great fighting commanders like George Patton and the man Truman called “Mr. Prima Donna, Brass Hat, Five Star MacArthur.”

Convinced that the vast majority of generals and admirals were “dumb,” Truman set out to bring them to heel by imposing meager budgets and by unifying the branches of the military. Yet the harder he pushed, the harder the generals and admirals pushed back. There would be no service unification. Then came the Korean War.

Not surprisingly, in 1950, when North Korea attacked South Korea, Truman impulsively committed the United States to war without asking the Joint Chiefs for their advice. Nor did he consult Congress. Had he done so, the chiefs doubtless would have been called to testify. They would have said that intervening in Korea was, in the words of Omar Bradley, chairman of the Joint Chiefs at the time, “The wrong war, at the wrong time, in the wrong place.”

Truman also ignored Chinese warnings that they would intervene if American forces came up to the Yalu River, the boundary between China and North Korea. In November, when MacArthur closed in on the river, the Chinese attacked with 300,000 battle-hardened troops, driving the Americans back.

The president who had been so quick to go to war suddenly was desperate for peace talks, but before Truman could craft a proposal to the Chinese, MacArthur launched a pre-emptive strike: he called on the Chinese to surrender or face annihilation. The Chinese responded by stepping up their offensive....