But the job comes with plenty of baggage, too. Cook has also had to navigate two Trump administrations and one Biden administration — each with its own posture toward Big Tech, China, and regulation. Cook also faced down the FBI over encryption, spent years in court defending the App Store against accusations that Apple had turned the iPhone into an illegal monopoly, and made compromises to stay in the Chinese market that attracted a whole lot of unwanted attention from human rights groups. Not last, Cook watched the company’s most ambitious hardware bet — the Vision Pro headset — bomb with consumers. That’s saying nothing of AI, where the outcome is still unknown. Incoming CEO John Ternus inherits all of it.

Here’s a walk through some of Cook’s biggest battles over the years.

Surely we all remember that 2016 FBI encryption fight? After a mass shooting at a holiday gathering in San Bernardino, California, the FBI demanded that Apple help unlock the gunman’s iPhone. Cook refused, arguing that encryption was the only meaningful countermeasure against exposing people’s private data and that being forced to break it would set a dangerous precedent. The standoff eventually ended when the FBI found another way in, but it cemented Apple’s identity as a privacy company and set up years of tension with governments around the world. Ternus will inherit that identity and the obligations that come with it.

The App Store antitrust wars haven’t been a walk in the park for Cook, either. Epic Games sued Apple in federal court over its requirement that apps use Apple’s in-app payment system and its 30% cut of sales (and when the judge pressed Cook on why users couldn’t simply pay developers directly at lower prices, his answers did little to deflect her skepticism). Apple largely prevailed in 2021, with the court declining to call it a monopoly, but it was ordered to allow developers to link to external payment options. It complied in the narrowest sense, charging a 27% commission on those external purchases (some discount!), and courts found it in contempt. The Ninth Circuit Court of Appeals upheld that ruling in late 2025, and after a rehearing request was denied last month, Apple is now preparing to petition the Supreme Court, which had already declined to hear its prior appeal. A lower court still must determine what fee Apple can actually charge.

The Epic saga is just one front in a much wider antitrust war. The U.S. Department of Justice sued Apple in March 2024, accusing it of unlawfully dominating the smartphone market by restricting third-party app and device developers — think competing smartwatches, digital wallets, and messaging services — in ways that make it harder for users to switch away from the iPhone. A federal judge denied Apple’s motion to dismiss that case, meaning it could grind through the courts for years. And just this week, Apple revealed it faces a potential $38 billion fine in India, where regulators have found it guilty of abusing its dominant position in the app market and say Apple has refused to hand over required financial data — a case complicated by the fact that Apple’s market share in India is still relatively modest, around 9%, giving it an unusual angle to contest the findings. Ternus inherits this fight mid-stream, with the App Store’s revenue model under direct judicial threat.

China has been a constant and increasingly uncomfortable balancing act, too. Cook built Apple’s manufacturing operation around Chinese supply chains, making the company deeply dependent on a country whose government grew both more assertive and less predictable over time. He also made uncomfortable concessions to operate in the Chinese market — most notably removing VPN apps from the Chinese App Store and storing Chinese users’ iCloud data on state-controlled servers. Cook proved adept during Trump’s first term at insulating Apple from tariffs and trade war risks, in part by cultivating a personal relationship with Trump — who remarked upon news of Cook’s retirement that he’s “an incredible guy!” Apple has already signaled that Cook will continue to help Ternus negotiate geopolitical terrain as executive chairman — an acknowledgment that these relationships are tricky and that Cook’s institutional knowledge remains highly valuable.

Yet AI is perhaps the most immediate and unresolved challenge that Ternus is being handed. Apple’s AI chief, John Giannandrea, formally leaves the company this month following numerous delays in the rollout of a more capable AI-powered Siri. Rather than relying solely on its own models, Apple has turned to both Google’s Gemini and OpenAI’s ChatGPT to power some Apple Intelligence features. Longtime market research analyst Bob O’Donnell told Reuters on Monday that Ternus’ biggest challenge will likely be “getting a better AI story and offering together that relies more on Apple’s own capabilities and less on third parties,” though some have argued that the company will look smarter in hindsight for waiting out the expensive competition playing out currently among today’s biggest AI outfits.

Last but not least, executive turnover at Apple more broadly is less discussed but meaningful. Ternus is inheriting a largely rebuilt leadership team following the recent departures of several other Apple execs over the last year, including its longtime COO, general counsel, and head of UI design. It’s a challenge and an opportunity that will require him to put his own stamp on things relatively quickly.

The through line connecting most of these challenges is that Cook’s greatest skill was his ability to manage complicated relationships with governments and partners while keeping the business humming. Whether Ternus has that same skill, or Cook’s continued presence as executive chair is meant to cover for any gaps there, may prove among the more interesting questions of the transition.

A much scarier question hanging over Ternus’ tenure is whether the world that made Apple the most valuable company on the planet could actually end. Many industry watchers believe AI agents will become the primary way people interact with services, rendering the App Store and its 30% cut a distant memory. Couple that with the possibility of compelling new hardware that erodes the iPhone’s grip on our lives, like whatever OpenAI has in the works, and Ternus could find himself maneuvering through much more than complex relationships and litigation.