In 1964 a certain Cassius Clay decided he was converting to Islam, setting in motion a chain of events that turned him into an icon around the world.

Despite the backlash he stuck to his guns, refusing to serve in Vietnam whilst being stripped of his boxing world titles.

His conversion to Islam has been subject to much conjecture, and now a new book says that it was actually a cartoon that really set the wheels in motion.

Ali: A Life, out in October, contains excerpts from a letter Ali wrote to his second wife, Khalilah Camacho-Ali. Below from TIME:

In the letter, which Camacho-Ali says her ex-husband wrote some time in the late 1960s, Ali describes seeing a cartoon in the Nation of Islam newspaper, Muhammad Speaks, outside a skating rink in his hometown of Louisville. The cartoon illustrated how white slave owners brutally beat their slaves, while insisting that they pray to Jesus.

Here’s that cartoon:

A transcription of some of that letter and its profound effect on Ali:

I did buy the Muhammad Speaks paper. And [one] thing in the paper [made] me keep the paper, and that was a cartoon. And the cartoon was about the first slaves that arrived in America, and the cartoon was showing how the black slaves were slipping off at the plantation to pray in the Arabic language facing the east. And the white slave master would run up behind the slave with a whip and hit the poor [slave] on the back with a whip and say, ‘what are you doing praying in that language, you know what I told you to speak,’ and the slave said, ‘yes sir, yes sir, Master. I will pray to Jesus, sir, Jesus.’ And I liked that cartoon. It did something to me. And it made sense.

Of course it’s not going to be one isolated incident that makes you reevaluate your religion, but author Jonathan Eig says that “this is the only time we know of that he wrote the story of his indoctrination in his own words”.

And now you know.

[source:time]