“He became a Muslim in 1964 after defeating Sonny Liston for the title,” Morton Susman, a United States attorney, said at the time. “In my opinion, his trouble started with that — this tragedy and the loss of his title can be traced to that.”

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Ali’s case went to the Supreme Court, which in 1971 reversed his conviction and agreed that he was deserving of conscientious objector status. After three years out of the ring, he returned to fighting and eventually regained his title.

The basketball player Mahmoud Abdul-Rauf became a flash point for controversy in 1996 when, playing for the Denver Nuggets, he declined to stand for the national anthem, citing American military aggression around the world.

“You can’t be for God and for oppression,” he said. “It’s clear in the Quran: Islam is the only way. I don’t criticize those who stand, so don’t criticize me for sitting. I won’t waver from my decision.”

After a brief suspension, he worked out a compromise that he would stand during the anthem but look downward and recite a Muslim prayer.

But Ali has long been the most visible Muslim athlete in the United States, even more so since Islam has become a political issue.

After the Sept. 11 attacks, Ali appeared on a celebrity telethon to defend his religion. He pleaded for acceptance and addressed the threat of terrorism, saying that terrorists killing in the name of Islam were wrong.

“People recognize me for being a boxer and a man of truth,” he said. “I wouldn’t be here to represent Islam if it was really like the terrorists make us look.”