It took 15 months and nearly $20 billion more than originally planned, but the Walt Disney Company has officially closed on its $71.3 billion purchase of 21st Century Fox, putting into motion one the industry’s most massive transformations ever.

The deal gives Disney control of the Twentieth Century Fox movie and TV studios, cable networks like FX and National Geographic, India’s Star network, and Fox’s 30 percent stake in the Hulu streaming service, as the company bulks up to take on Silicon Valley heavyweights like Netflix, Amazon, Apple and Google.

Just before the deal closed, 21st Century Fox spun off several of its assets—including the Fox broadcast network, Fox News, Fox Business Network and Fox Sports—into a new stand-alone company created Tuesday, called Fox Corp.

“This is an extraordinary and historic moment for us—one that will create significant long-term value for our company and our shareholders,” said Disney chairman and CEO Robert Iger in a statement. “Combining Disney’s and 21st Century Fox’s wealth of creative content and proven talent creates the preeminent global entertainment company, well positioned to lead in an incredibly dynamic and transformative era.”

Disney first announced its bid for Fox, which at the time was $52.4 billion, in December 2017. Comcast threw a wrench into talks last summer with its own counteroffer for Rupert Murdoch’s company, driving up Disney’s bid to $71.3 billion before bowing out in July.

The U.S. Justice Department approved Disney’s bid for Fox in July. As part of the DOJ’s approval, Disney agreed to divest Fox’s 22 regional sports networks, which were initially going to be part of the merger.

Shareholders from both companies approved Disney’s bid on July 27, but the deal still required regulatory approval in several international markets. Finally, last week, the companies said they would cross the finish line at long last on March 20.

Now that the merger has been finalized, both Disney and the new Fox will implement the leadership structures each company unveiled in October.

Peter Rice, who had been president of 21st Century Fox and chairman and CEO of Fox Networks Group, is now chairman of Walt Disney Television and co-chair of Disney Media Networks. He replaces Ben Sherwood, the co-chair of Disney Media Networks and president of Disney-ABC Television Group who is leaving the company.

Rice will oversee the ABC broadcast network, ABC Studios, the ABC-owned Television Stations Group, Disney Channels, Freeform, Twentieth Century Fox Television, FX Networks and FX Productions, Fox 21 Television Studios, and the National Geographic channels. Fox Television Group CEO and chairman Dana Walden is now chairman of Disney Television Studios and ABC Entertainment, and FX Networks and FX Productions CEO John Landgraf was named chairman of FX Networks and FX Productions.

Rita Ferro, named president of Disney advertising sales last September, will oversee all Disney media properties, including the new assets from Fox.

Meanwhile, the new Fox company is overseen by chairman and CEO Lachlan Murdoch. He tapped Marianne Gambelli to head up ad sales, with Joe Marchese, who had been president of advertising revenue for Fox Networks Group, departing the company as the deal closes. Gambelli had previously overseen ad sales for Fox News Channel and Fox Business Network.

Former AMC and SundanceTV chief Charlie Collier, who was named CEO of Fox Entertainment in October, oversees the Fox network. Eric Shanks, currently president, COO and executive producer of Fox Sports, has been named CEO of Fox Sports.

Collier said last month that Fox would be a “startup company” after it was spun off, albeit one with “$26 billion in valuation.”

For the past several months, many of the networks affected by the merger had found themselves in limbo, knowing what the post-acquisition plans were but unable to act on them until the deal closed. The situation was even more complicated with upfronts fast approaching.

“We have really strong public guidance, but we just can’t get into the nitty-gritty,” FX’s Landgraf told Adweek in February. “And the devil’s in the details.”

The timing of the potential close had disrupted some early upfront plans for networks that will be on the move to Disney. FX opted to skip its annual bowling party, which has been an upfront staple for a decade.

Now, however, Disney and new Fox are free to implement their respective game plans.

Disney will begin utilizing its new assets in the company streaming strategy, including Disney+, which CEO Bob Iger has said is Disney’s “biggest priority” this year and will launch in the fourth quarter. Hulu, which Disney owns a 60 percent stake in—the company is also in talks with AT&T to acquire its Hulu share, which would give it 70 percent—will also be a major focus, with FX and National Geographic content helping boost that service.

There is also the question of whether Disney will continue to give properties like FX Networks the same autonomy that it enjoyed under Fox, especially given AT&T’s recent decision to restructure WarnerMedia and remove the autonomy previously enjoyed by HBO and Turner (which prompted the departures of longtime HBO CEO Richard Plepler and Turner president David Levy).

Landgraf said in February that the more he has gotten to know Iger, “the more optimistic I’ve become about the future of FX.” Disney would like FX to increase its output, but Landgraf said those efforts will be “measured and focused,” and he and his team will maintain the quality of the FX brand.

The biggest fallout from the merger is still to come: the mass layoffs, projected to be at least in the 4,000-5,000 range, that will result from the acquisition.