That detail, revealed in a preview of his Good Morning America interview, is just one of several bombshells from the book, which comes out Tuesday. He also reportedly claimed that William and Kate Middleton urged him to wear the Nazi costume to a party in 2005 and that William physically attacked him in 2019 in a dispute over Meghan Markle.
In addition to upcoming interviews with Anderson Cooper for 60 Minutes and Tom Bradby for ITV in the U.K., the British royal sat for an interview with GMA's Michael Strahan, which airs Monday.
"You refer to your brother as your 'beloved brother' and 'archnemesis,'" Strahan asks him in a clip. "Strong words. What did you mean by that?"
"There has always been this competition between us," replied the younger son of King Charles and the late Princess Diana. "Weirdly. I think it really plays into or is played by the heir-spare" relationship, which puts William in line for the throne after Charles.
During the conversation, Harry told Strahan that he believes sharing "the truth" is what will eventually bring peace to the fractured relationship he has with his family.
"Ultimately, what this all comes down to is, I don't think that we can ever have peace with my family unless the truth is out there," said Harry, who left England in 2020 and settled in Markle's home state of California with their two children.
Strahan said he read the book cover to cover and promised jaws will drop when it is released. "He is not holding anything back," the co-anchor teased.
This comes amid leaks of the book to the press, including several wild stories. One, published by Page Six, claims that Harry put some of the blame for the infamous Nazi costume incident on his brother and sister-in-law. Harry, who was 20 at the time, wore the costume, that had a swastika on the arm, to a "Native and Colonial"-theme party, which William also attended.
Harry, who publicly apologized for the offensive display at the time and recently called it "one of the biggest mistakes of my life," said for the first time that his brother and Kate helped him pick the costume. He was between two: a pilot and a Nazi. William wore a homemade lion outfit.
"I phoned Willy and Kate, asked what they thought. Nazi uniform, they said," Harry wrote. When he went home and tried it on for them, "They both howled. Worse than Willy’s leotard outfit! Way more ridiculous! Which, again, was the point."
The outlet pointed out that royal historian Robert Lacey wrote in a 2020 book Battle of Brothers that the first sign of trouble in the relationship between the siblings came after the costume scandal. While William helped Harry choose the outfit, Harry didn't feel any support from his older sibling amid the public outrage over it. It left Harry feeling "alienated" and "resentful."
Meanwhile, The Guardian obtained an advanced copy of the book, publishing a story in which Harry claims William physically attacked him in Nottingham Cottage, where Harry and Meghan lived as newlyweds.
Harry said William came over to discuss "the whole rolling catastrophe" of their relationship. Markle wasn't present, but she was the topic with William reportedly calling his American sister-in-law "difficult," "rude" and "abrasive." Harry accused him of "parrot[ing] the press narrative" about the Suits actress — and that he expected better. William said he was trying to help Harry.
"Are you serious? Help me? Sorry – is that what you call this? Helping me?" Harry replied.
His response angered William, he claimed. He went to the kitchen of the tiny cottage — and William followed. He handed his brother a glass of water in hopes of calming him down, saying, "Willy, I can’t speak to you when you’re like this." He claimed that William set the water down and came at him.
"It all happened so fast," Harry wrote. "So very fast. He grabbed me by the collar, ripping my necklace, and he knocked me to the floor. I landed on the dog’s bowl, which cracked under my back, the pieces cutting into me. I lay there for a moment, dazed, then got to my feet and told him to get out."
William left but came back and apologized. He then asked Harry not to tell Markle what happened. Harry claimed he didn't right away, calling his therapist instead. He said Markle later noticed "scrapes and bruises" on his back, and he told her then of the fight and she was "terribly sad."
Harry also recalled a conversation with Charles and William after the funeral of Prince Phillip in April 2021. He claimed his father stood between them, seeing "our flushed faces" amid their tension and estrangement, and told them, "Please, boys. Don’t make my final years a misery."
Also among the leaks, the UK tabloid The Sun obtained a Spanish-version of the book. The outlet claims the dedication shades Charles and William as it says, "Para Meg, Archie y Lili… y, for supuesto, mi madre" — which translates to: "For Meg, Archie and Lili ... and, of course, my mother."
Meanwhile, new clips from Bradby's ITV interview this Sunday with Harry have been released. In one, he asked the prince, "Wouldn’t your brother say to you, ‘Harry, how could you do this to me after everything? After everything we went through?’ Wouldn’t that be what he would say?"
"He would probably say all sorts of different things," Harry replied.
Bradby also asked, "Some people will say you’ve railed against invasions of your privacy all your life and the accusation will be here are you invading the privacy of your nearest and dearest without permission."
Harry replied, "That would be the accusation from people that don’t understand or don’t want to believe that my family have been briefing the press," referring to his claim that the royal family has fed false stories about him and Markle to the press.
He also said he isn't sure he'll attend Charle's coronation in May — if he's even invited.
"There’s a lot that can happen between now and then," Harry said. "But, the door is always open. The ball is in their court. There’s a lot to be discussed and I really hope that they’re willing to sit down and talk about it."