President Franklin Delano Roosevelt was inaugurated for the fourth time on this day in 1945. He'd already broken the two-term precedent first set by President George Washington in his third inauguration, so a fourth was less groundbreaking in that sense — but it sure did freak out some people in Congress.
The inherent problem with traditions is that they don't always stick. FDR was wildly popular; he'd run for a third term on the back of his success pulling the economy out of the Great Depression. He became even more popular as he effectively steered the U.S. through most of World War II; by 1944, it was clear that the momentum was on the side of the Allies. Still, some worried that 16 years of being in office was too risky. That fear would be allayed when Roosevelt died three months into his fourth term, but members of Congress wanted to make sure the issue didn't crop up again. In 1951, the 22nd Amendment to the Constitution was ratified, codifying that presidents could serve only two terms.
You can read more about the 22nd Amendment in this article from History.com.
