Michael Beschloss is the author, most recently, of “Presidents of War.”

Against the challenge of the novel coronavirus, President Trump has said that he thinks of himself as a “wartime president.”

This is hardly the first time a president has used this metaphor, inexact as it may be. Richard Nixon asked Congress in 1971 to declare “war on cancer.” Lyndon Johnson in 1964 declared that his administration “here and now declares unconditional war on poverty in America." Poignantly, neither of those efforts came close to succeeding, but the strong language signaled a president aiming to mobilize the full resources of American society to conquer the problem.

One of the hallmarks of our system is that leadership in crisis must not only come from a president but also all reaches of society — in recent weeks, we have seen sparks of initiative from Congress, governors, the heroes of the emergency room and the research lab. We should all remember that from wartime presidential leadership we can learn as much from the mistakes as the accomplishments.

The history of U.S. wartime presidents offers seven lessons not only for Trump but also for leaders of all kinds:

Level with the public. James K. Polk in 1846 fabricated a reason to wage war against Mexico and lied to Congress and Americans about his intention to use that conflict to acquire almost 1 million square miles of new territory. When the 1918 flu broke out among U.S. soldiers, Woodrow Wilson disgracefully concealed the danger, kept sending troops to Europe and never gave a single speech about the pandemic that claimed 675,000 American lives and tens of millions abroad. At the start of major U.S. involvement in Vietnam in 1965, Johnson concealed from the public his dread that the war might grind on for a decade, take many lives and never be won.

Work to unite the country against the common enemy. War should not be a time for partisanship, yet James Madison waged the War of 1812 on the flimsy basis of a narrow congressional majority. Harry Truman never bothered to ask Congress for a war declaration against Korea. By contrast, after Pearl Harbor, Franklin D. Roosevelt, who had just won a third term from an electorate bitterly split over whether to fight Hitler or stay out, managed to make the World War II fight for freedom into the cause of almost every American.

Show empathy for the warriors, the scared and the suffering. Madison and Abraham Lincoln braved gunfire to visit scenes of battle. After the Spanish-American War, William McKinley went to Long Island to visit the tents of quarantined soldiers who had caught yellow fever while fighting in Cuba. Told that the mounting casualties of the Civil War required a new cemetery, Lincoln demanded that it be located near his summer cottage. He wished to make sure that he saw the burials and grieving families, so that the horrible, hourly decisions he was making about life and death would never become too abstract.

Build confidence in your plan for victory. Today FDR is remembered as perhaps the most successful war president of all time. But in early 1942, many Americans thought of him as the commander in chief who had made serious mistakes that culminated in the Japanese surprise attack. Thus, he spoke often in public and went on radio to explain the Allied blueprint to win the war. Before he spoke, the White House would ask Americans to buy world maps and globes so that they could follow along.

After the Soviets sneaked missiles into Cuba, John F. Kennedy knew he was facing not only a world crisis but also big domestic political trouble. He had assured Americans that there would be no such missiles in Cuba and made errors that had encouraged Nikita Khrushchev to put them there. But his TV speech revealing the presence of the missiles and his blockade plan to get them out was so shrewd and effective that to this day he is remembered not for his mistakes but for his mastery.

Warn of impending bad news as soon as you know about it. In 1942, two months after the attack on Pearl Harbor, FDR told Americans, “The news is going to get worse and worse before it gets better and better, and the American people deserve to have it straight from the shoulder.” Kennedy cautioned his TV audience that the Cuban missile crisis could last for months.

Trust wise, experienced experts. Lincoln fired Gen. George McClellan and finally promoted Ulysses Grant, to whom he gave considerable decision-making authority. Roosevelt prided himself on what he had learned about war as Wilson’s assistant secretary of the Navy, but he let Gen. Dwight Eisenhower run the D-Day invasion.

Stay focused and avoid mission creep. Madison let the 1812 war grow from a campaign to stop British harassment of U.S. ships into an effort to seize Canada. Polk’s Mexican War, ostensibly in response to a border skirmish, stretched almost 800 miles to Mexico City. LBJ inflated his effort to defend South Vietnam into a crossroads of the Cold War that threatened direct conflict with Russia and China.

A military confrontation is not the same thing as fighting a pandemic. No crisis in history ever provides an exact precedent for a challenge that a president is dealing with in real time.

But as Truman said, those in positions of authority must always be students of history. “Every leader," as he put it, "must be a reader.”

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