At the outset of 1944, Franklin D. Roosevelt was entering his 12th year as president of the United States.

The popular Democratic leader had steered his country through the Great Depression with his groundbreaking New Deal programs and won an unprecedented third term by a margin of some 5 million votes in 1940. Now, as another election year dawned, Roosevelt faced another monumental challenge: defeating Germany and Japan to win World War II, and negotiating with the Soviet Union to construct a lasting post-war peace.

Just as he did so, however, his health was deteriorating. Soon after returning from the Tehran Conference, Roosevelt developed a violent cough, began losing weight and was constantly fatigued. His daughter Anna was concerned enough to press Roosevelt’s personal physician, Dr. Ross McIntire, who arranged for the president to see Dr. Howard G. Bruenn, a cardiologist at Bethesda Medical Naval Hospital, for an examination on March 28, 1944.

According to Bruenn’s medical notes, which he later published, he diagnosed the 62-year-old Roosevelt with reduced lung capacity, hypertension (or high blood pressure), acute bronchitis and—most seriously—acute congestive heart failure.

At the time, medications had not yet been developed to manage hypertension, and the only treatment was regulating a patient’s lifestyle. In addition to a course of digitalis, an herbal drug extracted from leaves of the foxglove flower, Bruenn prescribed the president a restricted diet, reduced alcohol and tobacco use and increased rest. That meant that in May 1944—one month before D-Day—the daily schedule of the U.S. president included only four hours of work a day.

Under Bruenn’s regimen, some of Roosevelt’s symptoms improved, but he remained noticeably underweight. In July 1944, Dr. Frank Lahey, head of the Lahey Clinic in Boston, advised McIntire that he believed Roosevelt would not survive another full term in office. Lahey, one of a panel of medical experts who had examined Roosevelt that March after Bruenn’s diagnosis, also recorded his assessment in an unpublished memo, the full text of which would not be made public until more than six decades after Roosevelt’s death.

"It was my opinion,” Lahey wrote, “that over the four years of another term with its burdens, he would again have heart failure and be unable to complete it.”

According to Lahey, McIntire agreed with his assessment of the situation, although it’s unknown exactly how much information he passed along to his powerful patient. In any case, Lahey dated his memo on July 10, 1944. Ten days later, Roosevelt accepted the Democratic nomination for a fourth term as president.

The election of 1944 came at a precarious time for Roosevelt, his country and the world in general, and Roosevelt clearly felt a duty to see World War II through to its end. As Joseph Lelyveld argued in His Final Battle: The Last Months of Franklin Roosevelt, he was also desperate to avoid the fate of Woodrow Wilson, another president who had seen his country through a global conflict only to see his idealistic plans for lasting peace founder in the post-war years.

Now, Roosevelt believed he had to personally appeal to Soviet leader Joseph Stalin in order to ensure Soviet cooperation in both the war against Japan and in the founding of a new international organization: the United Nations. Only a solid relationship between the world’s two greatest powers, he was convinced, would effectively keep global peace.

Concerns about Roosevelt’s health among other Democratic leaders turned the question of his running mate in 1944 into a matter of much debate. Before accepting the nomination, Roosevelt decided to drop his vice-president, Henry Wallace, whom many saw as too left-wing and eccentric, from the ticket in favor of a Missouri senator, Harry S. Truman.

Though his Republican opponent, Thomas Dewey, undoubtedly benefited from widespread speculation about Roosevelt’s illness, Roosevelt managed to show enough stamina before the election to convince voters of his viability. In particular, he won points for a feisty speech about his dog, Fala, and toured New York City in an open car in the rain several weeks before Election Day. In November, he defeated Dewey handily, although by a closer margin in the popular vote than any of his previous wins.

In January 1945, Roosevelt traveled some 14,000 miles to the Yalta Conference, where he and Winston Churchill clashed bitterly with Stalin over the Soviet domination of Poland, among other issues. On March 1, a day after completing the arduous journey back to Washington, Roosevelt addressed a joint session of Congress to report on the conference. For the first time in his presidency, he appeared in public in his wheelchair.

After apologizing for delivering his speech from a seated position, he said he felt “refreshed and inspired,” and insisted that while Yalta was a good start, Congress and the American people would ultimately have the responsibility to follow through to create lasting peace.

“There can be no middle ground here,” Roosevelt declared. “We shall have to take the responsibility for world collaboration, or we shall have to bear the responsibility for another world conflict.”

At the end of March, Roosevelt left Washington for his retreat in Warm Springs, Georgia. On April 12, just 82 days into his fourth term, he died of a cerebral hemorrhage. Roosevelt’s sudden death left Truman, as his successor, to take the momentous step of using the atomic bomb against Japan, as well as to manage an increasingly tense relationship with Stalin.

It also sparked enduring controversies over Roosevelt’s deception of the American people, as well as whether his illness impaired his judgment and performance at a crucial moment during the Yalta Conference.

In the end, Roosevelt’s dream that the United Nations would prove to be an effective peacekeeping organization wouldn’t be realized. The Soviets didn’t, as he’d hoped, commit themselves to keeping peace alongside the United States. Instead, the post-war years saw the deterioration of American-Soviet relations, the fall of the Iron Curtain and the advent of a new titanic struggle in the Cold War.