Robinson didn’t suddenly become interested in civil rights and racial equality when Branch Rickey suggested he join the Brooklyn Dodgers. In fact, Robinson got into a few scuffles with authorities as a young man mainly because he refused to give in to the legal segregation known as Jim Crow in the South. This got him into a lot of trouble — and almost saw him dishonorably discharged from the Army.

As PBS reports, Robinson was on a military bus in 1944 and sat down next to the wife of a fellow officer. The bus driver, taking her to be a white woman, demanded that Robinson move to the back of the bus. When Robinson refused, things got ugly, and military police eventually arrived and arrested him. He was officially charged with “behaving with disrespect” toward a superior officer and “willful disobedience of lawful command” and had to defend himself at a court-martial.

Robinson argued his case passionately and was not afraid to call out the explicit racism that had sparked the incident. In the end, he was acquitted of both charges — but the legal proceedings meant that when his unit was sent into combat, Robinson wasn’t able to join them and thus never saw combat.

It can be difficult to believe today, but in the 1940s and 1950s, there was a real fear in the United States that communists were infiltrating our society and undermining our country. Nothing exemplified this paranoia more than the House Un-American Activities Committee (HUAC), led by Senator Joseph McCarthy. McCarthyism, as it has come to be referred to, leveraged the power of that committee to force people to denounce others in order to save themselves and ruined many lives in the process.

As Time reports, in late 1948, the general manager of the Brooklyn Dodgers received a call from an investigator for HUAC, who suggested that it would be good for Robinson to testify as a “friendly witness” in order to prove that he was a full-throated anti-communist. Robinson’s chance came a few months later when the athlete, actor, and singer Paul Robeson was accused of having stated that Black Americans would not fight for their country because of how they had been treated historically. (Robeson did not actually say this.) Robinson was called to testify.

Robinson attempted to thread the needle. He called Robeson’s supposed statement “silly” but used the opportunity to make several cogent points about racism and its negative impact on the country. Robeson was blacklisted, and his career was ruined, and Robinson later regretted his part in the hearing, saying, “I have grown wiser and closer to painful truths about America’s destructiveness.”

When Jackie Robinson stepped into a Dodgers uniform in 1947, he was officially a rookie player. In fact, that year, Robinson won the coveted Rookie of the Year Award — but he was hardly an inexperienced youngster. Robinson was 28 years old at the time and had already played several years of pro ball in the Negro Leagues.

As Sports Illustrated notes, being a 28-year old rookie is no small thing because a player’s peak age in terms of statistical ability is 27, meaning Robinson was already one year past his best playing years when he debuted. The average age of a baseball rookie is 24 years old, which means that at best, Robinson lost at least four years of playing time in the Majors. According to Baseball Reference, Robinson’s average yearly performance was a .311 batting average, 178 hits, 16 home runs, 86 runs batted in, 23 stolen bases, and a remarkable 111 runs scored. Four more playing years would have burnished his career totals nicely.

Segregation was only one reason Robinson started so late, of course — his military service during World War II was another. Even so, he came back to professional baseball in 1945. The effect the delay due to segregation had on his career is made clear when you consider the numbers he put up playing for the Montreal Royals in the International League: A .349 batting average with 40 stolen bases and 113 runs scored — the first two stats being career bests.

Jackie Robinson died in 1972 at the age of just 53. The official cause of death was a heart attack — his third in five years. But what really killed Robinson was diabetes.

Although Robinson’s family have always maintained that he was unaware of his diabetes until after he retired from baseball, as Sports Illustrated reports, it’s speculated that Robinson began experiencing the symptoms of diabetes when he was about 30 years old and that he was diagnosed in 1952, when he was 33. And The New York Times writes that Robinson experienced abnormally high blood pressure, a heart condition that worsened over the course of his lifetime, and progressive blindness that saw him lose vision completely in one eye. Curiously, Robinson didn’t like to talk about his condition — he doesn’t even mention the disease in his autobiography.

There’s little doubt that diabetes had a terrible impact on Robinson’s health. Not only was it clearly the ultimate cause of his early death, but it very likely contributed to his decision to retire from baseball in 1956 at the age of 37, just a few years after his diagnosis. His physical decline in the last decade of his life was remarkably swift and almost certainly attributable to this terrible disease.

Jackie Robinson achieved an amazing amount in his lifetime. He set athletic records, he served his country, he broke the color barrier in baseball, and he dedicated his life to pushing back against racism and prejudice. He was elected to the Baseball Hall of Fame, wrote a bestselling autobiography, and became a tireless agitator for racial equality in this country. It’s worth considering what else he might have done had he lived longer.

In fact, it’s astonishing to think that he not only achieved so much despite dying at age 53, but he did so despite spending the final decade of his life in increasingly worse health. Suffering from diabetes and a range of associated symptoms, like elevated blood pressure, blindness, and heart disease, Robinson was a gray-haired shell of the strapping athlete he’d once been.

Robinson remained clear-eyed about both his achievements and how much work was left to do. As Sporting News reports, Robinson’s autobiography I Never Had it Made was published just four days after his death and contains a quote that has become chillingly prescient: “I cannot stand and sing the anthem. I cannot salute the flag; I know that I am a black man in a white world. In 1972, in 1947, in 1919 at my birth, I know that I never had it made.”