Friday afternoon, President-Elect Donald Trump spoke on the phone with Taiwan’s new president Tsai Ing-wen, in the first known contact between leaders of both places since 1979, when the United States broke diplomatic relations with the island that China considers a province. In keeping with the “One China” policy, U.S. leaders have kept an ambiguous relationship with Taiwan and Taiwanese leaders—engaging in trade with Taiwan and offering it protections while adhering to the People’s Republic of China’s position.

Trump’s phone call with Taiwan’s president on Friday prompted a few questions. First: did Trump even know he was breaking with the official policy of the United States? And when, if ever, will the president-elect begin adhering to normative practices for communications between world leaders?

Kellyanne Conway told CNN Friday night that Trump had been “fully briefed” on U.S.-Taiwanese relations before taking the call. Former George W. Bush administration spokesman Rich Grenell said that the call was “totally planned,” and that it was “a simple courtesy call.” In what is surely totally unrelated news, Trump had reportedly been considering hotel investments in Taiwan earlier this year.

Presidential diplomatic phone calls are a tricky business. Here’s how the Obama administration dealt with making calls, from this Yahoo News article from 2014:

Before Obama calls another world leader, an aide brings him a specially prepared National Security Council dossier. The package includes a closely held American intelligence portrait of the person he’s going to call — including highly personal information about their personality, their health and their loved ones. “Are they cool-headed? Or the opposite? Do they like to joke?” said one source familiar with the contents of the dossier.

“The world leader profiles include basic intel, idiosyncrasies, personal political pressures, whether any close relatives are seriously ill, girl- or boyfriend problems, personal health issues,” said another official.

Calls with Chinese leaders involved their own set of complications, because they usually start with what one source described to Yahoo as “a restatement of America’s Chinese policy,” a series of talking points which include a reassurance that the United States “believe[s] the future of Taiwan should be resolved peacefully.”

There are, naturally, some differences between the actions of a president and a president-elect. But Trump’s call is already not without consequence. On Saturday, China said it had lodged an official complaint with the U.S. government over the phone call. According to a White House spokesman, the two leaders spent the call simply congratulating each other on their recent victories, but even a small action like this can have wide-ranging ramifications.

The U.S. and China’s “One China” policy has been in place since 1972, when Nixon visited the country. Jimmy Carter recognized Beijing as the legitimate government of China in 1978, and in 1979 the U.S. closed its embassy in Taiwan.

“This phone call calls into question whether or not Trump adheres to the basic foundation of the U.S.-China relationship,” Barack Obama’s former top China adviser Evan Medeiros said. “This action guarantees that U.S.-China relations under Trump will get off to a very rocky start.”

On Friday night, however, Trump tweeted that he thought the call was simply no big deal.