Just days after the United States joined World War I, former President Teddy Roosevelt dropped by the White House to see the sitting Commander in Chief, Woodrow Wilson. Eight years after his own presidency, and 19 years after his cavalry charge on Cuba’s San Juan Hill, the ever bombastic 58-year-old Roosevelt wanted to go to war again.

For months, as the U.S. had edged toward war with Germany, Roosevelt had been trying to form a new version of his Rough Riders, the all-volunteer division that he’d led in the Spanish-American War. Now, on April 10, 1917, the pugnacious ex-president had the chance to sell the idea of a reconstituted Riders to Wilson, the cautious academic who’d defeated him in the 1912 presidential election.

Wilson greeted Roosevelt warily. Their rivalry, cooled by a friendly White House chat over lemonade three years prior, had flared up the previous fall. Campaigning for Wilson’s opponent, Republican Charles Evans Hughes, in November 1916, Roosevelt blasted Wilson as cowardly for not going to war over the German sinking of the Lusitania. Privately, in the months since the election, he’d kept it up. On March 1, the day news of the Zimmermann Telegram broke, he’d sniped to his son Kermit about “the lily-livered skunk in the White House.” But now that Wilson had chosen war, Roosevelt tried to reconcile.

“Mr. President, what I have said and thought, and what others have said and thought, is all dust in a windy street if now we can make your [war] message good,” Roosevelt said.

Even the reserved Wilson couldn’t resist Roosevelt’s effusive charm. “The president doesn’t like Theodore Roosevelt and he was not one bit effusive in his greeting,” White House staffer Thomas Brahany wrote in his diary. But soon, Brahany added, “the President had ‘thawed out’ and was laughing and ‘talking back.’ They had a real good visit.” Roosevelt promised to support Wilson’s proposal for a military draft, then hit him up with his request to return to the Army as a division commander. “I told Wilson that I would die on the field of battle,” Roosevelt said later, “that I would never return if only he would let me go!”

After their 45-minute talk, Roosevelt left in a whirlwind of handshakes and backslaps with longtime White House employees. “The president received me with the utmost courtesy and consideration,” Roosevelt told reporters on the White House steps, adding that he hoped his proposed division could be “part of any expeditionary force to France.”

All that afternoon and evening, the British, French, and Japanese ambassadors and various congressional committee chairmen crowded into the Washington townhouse of Roosevelt’s son-in-law, Representative Nicholas Longworth. Roosevelt talked up his plans to ride again. Secretary of War Newton D. Baker, whom Roosevelt had already lobbied by letter, also visited, after a nudge from Teddy’s distant cousin, assistant navy secretary Franklin D. Roosevelt. “I am aware that I have not had enough experience to lead a division myself,” Roosevelt admitted. “But I have selected the most experienced officers from the regular army for my staff.” Baker told Roosevelt he’d think about it.

Two days later, on April 12, Roosevelt started lobbying Congress to pass legislation allowing volunteer divisions to fight in Europe. He wrote to the chairman of the Senate Military Affairs Committee that privately organized divisions could get the U.S. into the fight sooner than a draft. “Let us use volunteer forces, in connection with a portion of the regular army, in order at the earliest possible moment, without a few months, to put a flag on the firing line,” he wrote. “We owe this to humanity.”

Roosevelt wouldn’t take no for an answer. Baker denied his request on April 13, writing that commands would go to longtime officers who “have made a professional study of the recent changes in the art of war.” Roosevelt responded with an 15-page letter to Baker, arguing that the war secretary’s advisers were “well-meaning men, of the red-tape and pipe-clay school, who are hidebound in the pedantry” of “wooden militarism.”

But Roosevelt’s bravado and self-confidence failed to move Baker. The former president proposed leading a volunteer company, including a cavalry brigade, after six weeks of stateside training, followed by “intensive training” in France. Baker’s next reply made it clear that he thought Roosevelt’s idea foolhardy and naïve. If the U.S. deployed “hastily summoned and unprofessional” volunteers to the front, Baker wrote, the Allies would be “depressed by the dispatch of such a force, deeming it evidence of our lack of seriousness about the nature of the enterprise.” Stubbornly, Roosevelt wrote back yet again, insisting that he’d be as successful a commander as he was in 1898. Volunteers, he argued, could become “almost as good” as the regular army after training on “bayonet work, bombing, gassing, and all the other elements of modern trench warfare.”

Future president Warren G. Harding, then a U.S. Senator, took up Roosevelt’s proposal, sponsoring a draft-bill amendment to authorize four volunteer divisions. The legislation didn’t mention Roosevelt, but Congress knew it was written with him in mind. “He is known in Europe as no other American,” argued Sen. Henry Cabot Lodge. “His presence there would be a help and an encouragement to the soldiers of the allied nations.”

By early May, 2,000 men a day were writing to Roosevelt, offering to volunteer. He lined up a dream team of scrappy commanders, including former Rough Rider John Campbell Greenaway, Louisiana politician John M. Parker, and frontier marshal Seth Bullock. Blind in his left eye and prone to bouts of malarial fever, Roosevelt had no illusions that he’d emerge triumphant, or even alive, from the battlefield. As vividly depicted in Edmund Morris’ 2010 biography Colonel Roosevelt, his hopes to return to battle were a mix of ardor and fatalism. “I shall not come back,” he told fellow Republicans in New York.

Congress approved Harding’s amendment to the Selective Service Act. French envoy Marshal Joseph Joffre lobbied Baker to let a division fight under Roosevelt’s command alongside France’s troops on the Western Front.

But Wilson decided against it. He and Baker wanted to fight with a “people’s army,” representative of the nation, built by universal conscription. He also distrusted Roosevelt, despite the man’s personal charm.

“I really think the best way to treat Mr. Roosevelt is to take no notice of him,” Wilson wrote his personal secretary, Joseph Tumulty. “That breaks his heart and is the best punishment that can be administered. After all, while what he says is outrageous in every particular, he does, I am afraid, keep within the law, for he is as careful as he is unscrupulous.”

Wilson thought Roosevelt was looking for publicity and “wanted to use the Army’s best officers to make up for his own shortcomings,” wrote Arthur Walworth in his 1958 biography of Wilson. And according to H.W. Brands’ 2003 Wilson bio, the president may have even feared that Roosevelt could win back the White House in 1920 if he became a war hero again.

On May 18, 1917, Wilson signed the Selective Service Act. It gave him the power to conscript men ages 21 to 30 – and the option of calling up 500,000 volunteers. In an exceedingly polite statement issued after the signing, the president announced he would allow no special volunteer divisions in the war.

“It would be very agreeable for me to pay Mr. Roosevelt this compliment, and the Allies the compliment, of sending to their aid one of our most distinguished public men,” Wilson declared in his written statement. “But this is not the time… for any action not calculated to contribute to the immediate success of the war. The business now at hand is undramatic, practical, and of scientific definiteness and precision.”

Wilson sent Roosevelt a telegram, claiming he’d based his decision on “imperative considerations of public policy and not upon personal or private choice.” Roosevelt didn’t buy it. Convinced Wilson had snubbed him out of jealous rivalry, he went back to trashing the president in private, calling him in one letter “an utterly selfish, utterly treacherous, utterly insincere hypocrite.” But Roosevelt released a notice dismissing his would-be volunteers. “Never, except in a house of death, have I noticed a greater air of depression,” wrote a reporter who visited him then.

By World War I’s end in November 1918, 2 million soldiers served in the American Expeditionary Forces in Europe. All four of Roosevelt’s sons joined the military and went to the front. His sons Archie and Ted were wounded in battle, and his youngest son, Quentin, a pilot, was shot down and killed in July 1918. “Am greatly distressed that your son’s death is confirmed,” Wilson telegrammed Roosevelt. “I had hoped for other news.” Roosevelt’s last months were a torrent of emotions: pride in his sons’ battles and grief over Quentin’s death. He dictated a skeptical editorial for the Kansas City Star about Wilson’s proposed League of Nations three days before his death on January 6, 1919.