Rupert Murdoch is stepping down as the chairman of Fox Corporation and News Corp. - the business empire he once vowed to leave "feet first" - ending a 70-year career that saw him rise from publisher of a small Australian newspaper to become a driving force in global conservative media and politics.

In a memo to employees Thursday, Murdoch, 92, announced plans to become chairman emeritus at both companies. His son Lachlan, 52, will become the sole chairman of News Corp. - which oversees the Wall Street Journal as well as other print and digital media properties - and continue as executive chairman and CEO of Fox Corporation.

Murdoch's blending of news and entertainment reshaped the norms of an entire industry. His willingness to use his outlets to advance his political and business interests - most notably with Fox News - made him a figure of admiration and fear, his counsel sought by politicians and business leaders.

But his exit comes after a challenging period for the companies and their founder. Fox's record-breaking $787.5 million settlement of a defamation lawsuit in April came after a meandering deposition by Murdoch, in which he acknowledged he had done nothing to stop Fox News hosts from airing baseless accusations of vote-rigging in the 2020 presidential election. Shortly thereafter, Fox fired popular opinion host Tucker Carlson, leading to a downturn in ratings.

Despite decades of mutually beneficial relationships with politicians, the Murdochs have struggled with how to navigate their complicated relationship with former President Donald Trump - a candidate whose fortunes Fox News bolstered in 2016 but on whom the elder Murdoch has soured in recent years.

Yet Fox News remains the top-rated cable news channel and has seen some of its post-Carlson losses reversed with a new prime-time lineup.

While a family succession plan has been more or less set for several years - Lachlan Murdoch's younger brother, James, left the company in 2020 - the handoff to the next generation came as something of a surprise.

Rupert Murdoch had seemed reluctant to scale back his work schedule. When he beat prostate cancer in 2000, he famously quipped, "I'm now convinced of my own immortality," and he often reminded people that his mother, Dame Elisabeth Murdoch, lived until 103.

"Our companies are in robust health," Murdoch said in his parting statement to employees Thursday, "as am I."

He was in the company's Los Angeles office every day this week and was seen walking through the Fox lot, according to a person familiar with his movements. His deep ongoing involvement in his media properties was on display over the past several months, not just with the firing of Carlson - whose increasingly anti-Ukraine on-air rhetoric and behind-the-scenes disrespect for Fox executives bothered Murdoch - but also with the hiring of Emma Tucker, a veteran of the U.K. Sunday Times who was close to Murdoch's inner circle, as editor in chief of the Journal.

Yet he has also struggled with health issues in recent years, including a serious fall and a dire case of COVID-19. Last year, he divorced his fourth wife, the former actress and model Jerry Hall, and then became briefly engaged to another woman before breaking up weeks later.

Murdoch took his inheritance at age 21 of a single newspaper in Adelaide and built it into a world-spanning media empire that, in addition to Fox News and Fox Sports, includes the New York Post, publishing giant HarperCollins, and the British newspapers the Sun and the Times.

In 1985, he became a naturalized citizen to satisfy the requirement that only American citizens were permitted to own U.S. television stations. He created Fox broadcasting and Fox News, upending both industries. His net worth is estimated at between $8.26 billion (according to Bloomberg News) and $17.4 billion (according to Forbes).

But his empire had suffered a number of blows, starting with a phone-hacking scandal that enveloped his British newspapers in 2011 - leading to the closure of his News of the World tabloid, resignations and prison time for some of his top executives, and the loss of major business opportunities, such as an attempt to buy full control of satellite broadcaster BSkyB.

Two years later, Murdoch split his beloved News Corp. in two, a move that sequestered the seemingly toxic assets of his British newspapers from his television and movie properties, which were rebranded as 21st Century Fox. Nonetheless, Murdoch sold the bulk of 21st Century Fox to Disney for $71.3 billion in 2017 - motivated in part by a daunting competitive landscape as well as his inability to get Lachlan and James to agree on a plan for the company's future, according to people familiar with the family's dynamics who spoke on the condition of anonymity to discuss private family deliberations. The remaining company, branded Fox Corporation, was composed primarily of Fox News, Fox Sports and Fox television stations.

While Murdoch dreamed of reuniting the two halves of his empire under the same corporate structure, an attempt to make that happen fell short this year after major shareholders balked.

His decision to step down solidifies Lachlan Murdoch's executive role atop the two companies. Rupert Murdoch still retains his position in the family trust that controls the business, holding four votes of his own while his adult children - Lachlan, Elisabeth, James and Prudence - each have a single vote. When he dies, each of them will have an equal vote in the future of the family empire. Murdoch's two youngest, college-age children, with his third wife, Wendi Murdoch, have no voting power in the trust.

While Lachlan Murdoch has shied away from the kind of political relationships his father cultivated, they share a conservative ideology. In his parting note to staff - which took characteristic swipes at "self-serving bureaucracies" and "elites" - Rupert Murdoch wrote that his own father "firmly believed in freedom, and Lachlan is absolutely committed to the cause."

Even though his father's retirement solidifies his position, Lachlan Murdoch may not have a stranglehold on the company's future. People close to James Murdoch - whose politics are decidedly more centrist than that of his father and brother - have privately floated the idea that after Rupert Murdoch's death, James could attempt to rally his sisters and outside investors to his vision of Fox News as a more center-right outlet.

Current and former executives of Fox also privately cite the possibility of a sale of the company, something that felt nearly impossible when Rupert Murdoch was CEO.

"With Murdoch, Fox News faces a situation more perilous than the typical executive succession," said Lynne Vincent, an associate professor at Syracuse University's Whitman School of Management. "Typically, the longer the tenure of the executive, the trickier and more challenging the transition will be."

Murdoch's legacy in business and media will be intertwined with that of the increasingly far-right politics espoused by Trump and the opinion hosts on Fox News who championed him.

Murdoch was never a full-throated supporter of Trump. But once the New York real estate magnate solidified his position as the Republican front-runner in the 2016 race, Murdoch and Fox both settled in for a mutually beneficial ride. The sale to Disney sailed through with no regulatory pushback from the Trump administration, and Trump had a seemingly open invitation to appear on Fox News.

But their relationship started to cool in the months leading up to the 2020 election. Murdoch disapproved of Trump's handling of the coronavirus pandemic and started telling associates that he felt Trump was likely to lose the race to Joe Biden. The night that Fox News projected that the state of Arizona would flip for Biden, an infuriated Trump directed son-in-law Jared Kushner to implore Murdoch to reverse the call. Murdoch declined, and Trump became increasingly vocal in his criticism of Fox News.

But to win back its Trump-supporting audience, some of Fox's hosts advanced Trump's false claims of election fraud, leading the company into legal peril, even as executives behind the scenes hoped to break from the former president.

Documents uncovered this year in the blockbuster defamation lawsuit from Dominion Voting Systems revealed that Murdoch and other top executives harbored animosity toward Trump, both before and after the Jan. 6, 2021, attack on the U.S. Capitol by the outgoing president's supporters.

In early 2021, Murdoch wrote in a private email that he hoped "to make Trump a non person." Fox News board member Paul D. Ryan, a former House speaker, told a Fox executive around the same time that both Rupert and Lachlan were on board with what they saw as a "huge inflection point to keep Trump down and move on."

For a while, Murdoch's media properties seemed to lavish more attention on a key Trump challenger for the 2024 GOP nomination, Florida Gov. Ron DeSantis.

More recently, though, Murdoch made direct, personal appeals to Republican Gov. Glenn Youngkin of Virginia to run for president, The Washington Post reported last month.

Meanwhile, Trump has continued to engage with Fox News, though the relationship remains fraught and he frequently bashes the network and the family that runs it - notably after a tough interview by Fox News anchor Bret Baier over the summer.

Murdoch was known throughout his career as an avid gossip and workaholic. He regularly called his top news executives to weigh in on the news of the day.

And his parting memo to staff indicated that may not change, even after retirement.

"I will be watching our broadcasts with a critical eye, reading our newspapers and websites and books with much interest, and reaching out to you with thoughts, ideas, and advice," he wrote. "When I visit your countries and companies, you can expect to see me in the office late on a Friday afternoon."

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Will Sommer contributed to this report.