The billionaire Bill Ackman has dominated headlines lately for his bare-knuckle fights against Ivy League schools and the media.

He has called for the firing of top university heads, excoriating them for the way they responded to Israel-Hamas conflict, and condemned them for promoting diversity, equity and inclusion, or DEI.

In long screeds on X, formerly known as Twitter, he has amplified plagiarism allegations against Claudine Gay, who stepped down from Harvard's presidency under pressure. Most recently, Ackman has threatened to sue a news organization that published several pieces that accused his wife of plagiarism.

This is classic Ackman. He likes to fight, he digs in, and he doesn't give up.

In 2013, when a journalist asked him how long he was prepared to stick with one of his boldest — and ultimately ill-fated — bets, Ackman was resolute.

"I'm going to the ends of the earth," he said.

Ackman's tactics "disgusted" one top exec

Over three decades, Ackman has gone to war against companies, executives, and other high-profile investors, and developed a reputation for being ruthless and relentless.

He has infuriated many of them. Howard Schultz, the former Starbucks CEO, once said he was "disgusted" by Ackman's tactics of firing off a public three-page letter urging JCPenney's board to replace its top executive. Billionaire investor Carl Icahn once dubbed Ackman "a major loser," and said on TV that he was either "the most sanctimonious guy I ever met in my life, or the most arrogant."

None of this has stopped Ackman, who is now using the same cutthroat techniques he honed at Pershing Square, the hedge fund he founded in 2004, against a long list of new targets.

The battle against Herbalife lasted six years and big losses

One of the most famous corporate fights Ackman waged was against Herbalife, a company that makes nutritional supplements.

In 2012, Ackman bet $1 billion against the company. In an elaborate three-hour presentation he called it a pyramid scheme. That was just the beginning of a scorched-earth campaign to convince other investors — and regulators — he was right.

Rival investor Icahn didn't agree with Ackman's assessment, and the two argued live on CNBC. In the world of business television, that interview was akin to WrestleMania.

"He is like the crybaby in the schoolyard," Icahn said. "You know, I went to a tough school in Queens, and they used to beat up the little Jewish boys, and he was like one of these little Jewish boys crying that the world was taking advantage of him." (Both Icahn and Ackman are from New York, and of Jewish descent.)

Icahn soon after that interview revealed that he had made the exact opposite bet, and purchased more than 13% of Herbalife shares.

Ackman lost a lot of money on that wager, but he held on to that fight for years, even as it became clear that the odds were against him.

Letters and presentations in railroad fight ends in resignations

Of course, Ackman's tenacity has made him a billionaire many times over and also won him fans. For instance, in a 2013 column for "The New York Times," corporate law professor Steven Davidoff Solomon referred to him as "a brilliant investor by any measure."

Ackman often takes on companies that he believes hide their financial woes. His tactics are the same, and he's won some big fights against well-known businesses.

For instance, in 2011, his fund Pershing Square bought more than 14% of Canadian Pacific Railway's stock, giving him a lot of sway. In a meeting with the company's CEO and board chair he told them he was eager to clean house.

The railroad company's executives didn't agree, and the two sides fired shots at each other for months. Ackman appealed to other investors with a flurry of presentations and letters, and the company replied in kind.

In a memorandum to his fellow stockholders, Ackman wrote, "The incumbent board and management have failed shareholders, employees and customers."

Not being able to withstand the relentless pressure, the company's chief executive resigned, and several other board members opted not to stand for re-election on May 17, 2012, right before the company's annual meeting was scheduled to begin. Reuters called it "a boardroom coup."

Ackman's handpicked candidates won, and together, they engineered a corporate turnaround.

How Ackman is using the same playbook now

This time, Ackman isn't focused on corporate governance; instead, he has his sights set on broader, cultural changes. But Ackman's methods are the same.

Since October, Ackman has written three memos to Harvard's governing board, which he has shared with his million-plus followers on X. His campaigns often begin with detailed and lengthy public letters.

"Let's make a deal," he wrote in a post addressed to M.I.T.'s governing board, as he campaigned for the removal of that university's president, Sally Kornbluth. "If you promptly terminate President Kornbluth, I promise I won't write you a letter."

Ackman has traveled to Cambridge, Mass., to meet with students and faculty at Harvard, spoken with a handful of reporters at major news organizations, and done two live interviews with CNBC about his latest crusade. He has declined several requests for an interview with NPR.

Broadly speaking, Ackman believes that academia has lost his way. What started as a critique of how Harvard's president reacted to student protests in the aftermath of Hamas' attack on Israel has broadened.

Since October, Ackman has denounced Harvard and several other academic institutions for how they address antisemitism, and he has attacked public policy, including DEI.

"Racism against white people has become considered acceptable by many not to be racism," he wrote in an essay after Gay Stepped down. "It has become the prevailing view in many universities across the country."

Ackman has called on Harvard to shutter its Office for Equity, Diversity, Inclusion, and Belonging.

"DEI is racist," he wrote, adding "the DEI movement is an important contributor to our growing divisiveness."

Earlier this month, Ackman launched a new salvo against the media after Business Insider identified what it calls "a pattern of plagiarism" in academic writings by his wife, the designer Neri Oxman.

In a series of posts, some of which are thousands of words long, Ackman criticized the reporters and editors involved, and exhaustively detailed how he attempted to get board members and executives to remove the articles from Business Insider's site.

Ackman said he's planning to sue Business Insider and its parent company, the German media conglomerate Axel Springer.

He's trying to sway presidential hopefuls too

Ackman has also turned his attention to Washington, hoping to influence presidential politics, donating to several candidates, including Robert F. Kennedy, Jr., former Gov. Chris Christie, and Vivek Ramaswamy.

On Jan. 13, Ackman threw his support behind Rep. Dean Phillips, a Minnesota Democrat who is waging an outside campaign against President Biden in the Democratic primaries. Ackman pledged $1 million to support Phillips, and participated in a public conversation with the congressman on X.

Shortly thereafter, one of Ackman's followers noted Philipps had a page on his campaign website devoted to "diversity, equity, and inclusion."

"How do you justify this?" the X user wrote to Ackman.

"He didn't understand DEI until recently," he replied. "I expect that statement will be revised promptly."

As "The New York Times" reported, later that day, that mention of diversity, equity, and inclusion was gone.