For much of his adult life, Franklin D. Roosevelt battled chronic health problems that could have derailed his political career. Instead, his personal suffering transformed him into a more empathetic politician and steeled him to confront the dual challenges of the Great Depression and World War II.

Death had almost taken Roosevelt before he drew his first breath. When his mother was administered a chloroform overdose during an agonizing labor that lasted more than 24 hours, the future president was born blue, limp and lifeless until a doctor revived him through mouth-to-mouth resuscitation.

The traumatic birth left no lingering effects. Aside from being uncommonly susceptible to respiratory and sinus infections, Roosevelt remained vigorous as his political star ascended—until tragedy struck on August 10, 1921. Vacationing with his family on Campobello Island off the Maine coast, the 39-year-old Roosevelt enjoyed a summer day full of sailing and swimming. However, he skipped dinner and went to bed early after feeling chills and lower back pains.

Roosevelt awoke to a life that would never be the same again. “When I swung out of bed my left leg lagged,” he recalled. “I tried to persuade myself that the trouble with my leg was muscular, that it would disappear as I used it.” It didn’t. For two weeks, the spreading paralysis and severe pain baffled local doctors until a specialist from Boston delivered the diagnosis—polio.

Left paralyzed from the waist down, the optimistic Roosevelt never lost hope that he would regain the use of his legs and return to politics. “I’m not going to be conquered by a childish disease” he vowed.

He found respite in the therapeutic mineral waters of Warm Springs, Georgia. Meeting others stricken by polio at Warm Springs altered Roosevelt, says David B. Woolner, author of The Last 100 Days: FDR at War and at Peace and a senior fellow at the Roosevelt Institute. “It had an enormous impact in deepening his sense of compassion for people less fortunate than himself and exposed him to rural poverty in the Southeast, which later partially inspired him to launch the Tennessee Valley Authority.”

Unable to regain the ability to walk under his own power, Roosevelt engaged in what biographer Hugh Gallagher called a “splendid deception” to make it appear as if he could walk, lest voters viewed him as incapacitated. Through perseverance and physical therapy, Roosevelt learned to stand upright with heavy steel braces clamped to his withered legs. He would swing his hips forward and grip tightly to a cane and the arm of a family member or aide to “walk” a few painstaking steps and deliver speeches standing up while clinging to a lectern.

While Roosevelt’s polio was no secret during his successful 1928 campaign for governor of New York, he carefully cloaked his disability in public. The press agreed not to photograph or film him in his wheelchair or being lifted out of automobiles.

Elected president in 1932, Roosevelt brought the same optimism and resolve to addressing the Great Depression as he did to his polio symptoms. He attempted to instill hope among the hopeless from the very start of his presidency by declaring in his first inaugural address, “The only thing we have to fear is fear itself.”

Roosevelt’s health began a steep decline after his nearly 18,000-mile roundtrip to the Tehran Conference in November 1943 to meet British Prime Minister Winston Churchill and Soviet Premier Joseph Stalin on strategy to fight Adolf Hitler. Upon his return, an ailing, exhausted Roosevelt lost weight, and his trembling hands struggled to light cigarettes, sign documents or pour coffee.

The president’s physician, Dr. Ross McIntire, insisted to the press that Roosevelt was in “robust health” and his stamina was “far above average.” But the commander-in-chief’s daughter, Anna, was skeptical. At her behest, McIntire—an ear, nose and throat specialist—arranged for Dr. Howard Bruenn, Bethesda Naval Hospital’s top cardiologist, to examine Roosevelt in late March 1944.

Bruenn delivered a shocking diagnosis: The president was suffering from severe hypertension and congestive heart failure. Roosevelt was prescribed the herbal drug digitalis, placed on a restricted diet, told to restrict his smoking to six Camel cigarettes a day and advised to work only four hours a day—an impossibility for a wartime president.

Although Bruenn had been assigned to monitor Roosevelt, McIntire reported in early June 1944 that the president’s health was “excellent in all respects.” Prominent surgeon Dr. Frank Lahey, who consulted on the president’s condition, hardly agreed and informed McIntire in early July that he “did not believe that, if Mr. Roosevelt were elected President again, he had the physical capacity to complete a [fourth] term.”

McIntire certainly concealed Lahey’s prognosis from the public, and he may have done the same with his patient. “I suspect McIntire didn’t bluntly tell him he wasn’t going to survive, but Roosevelt understood he had a heart problem,” Woolner says.

Days after Lahey’s dire assessment, Roosevelt announced he would accept the Democratic nomination for an unprecedented fourth term. He wanted to see the war to its conclusion and realize his plan to establish the United Nations.

Two days after taking the oath of office for the fourth time on January 20, 1945, Roosevelt departed on an arduous five-week journey to meet again with Churchill and Stalin at the Yalta Conference.

While Cold War critics later derided Roosevelt as “the sick man of Yalta” who yielded too many concessions to Stalin, Woolner asserts the president’s mind remained sound at the conference. “There’s no question when you look at the records and minutes that Roosevelt was completely in charge of his faculties,” he says. “His comments reflected the State Department briefing papers verbatim.”

Roosevelt displayed a rare openness about his disability when he addressed a joint session of Congress on March 1 upon his return from Yalta. For the first time in his presidency, he appeared in public in his wheelchair as Secret Service agents pushed him into the House of Representatives chamber. Roosevelt apologized for not standing up to speak. “I hope that you will pardon me for the unusual posture of sitting down,” he said. “But I know that you will realize that it makes it a lot easier for me in not having to carry about ten pounds of steel around on the bottom of my legs.”

A gaunt Roosevelt returned to Warm Springs at the end of March. “The president was the worst-looking man I ever saw who was still alive,” recalled the town’s stationmaster. On the afternoon of April 12, Roosevelt’s blood pressure soared to 300/190. he proclaimed before slumping forward in his wheelchair. Those words were Roosevelt’s last as he died of a cerebral hemorrhage at the age of 63. The news shocked a nation that never knew how ill its president had been.