The Washington Post reports Donald Trump's call with Taiwan's president was "the product of months of quiet preparations," according to sources.

Many criticized Donald Trump after reports surfaced that he had engaged in a phone conversation with Taiwan's president. And quite a few assumed it was a thinly-thought through action by the president-elect without a full understanding of the diplomatic structure in place.
However, a report by the Washington Post suggests that Trump's call may have been much more deliberate.
According to the Post, the phone conversation "...was an intentionally provocative move that establishes the incoming president as a break with the past, according to interviews with people involved in the planning."
Further, the publication notes, it was "...the product of months of quiet preparations and deliberations among Trump’s advisers about a new strategy for engagement with Taiwan that began even before he became the Republican presidential nominee, according to people involved in or briefed on the talks."
Trump's call with Tsai Ing-wen marks a departure from the U.S. foreign policy which, for decades, has sided with China in viewing Taiwan as a province, not a sovereign nation.
Chinese officials have lodged a diplomatic complaint in response to the call and reiterated in a statement, “The 'one China' principle is the political foundation of China-US relations.”
Meanwhile, Trump defended the conversation on Friday, posting to Twitter, “The President of Taiwan CALLED ME today to wish me congratulations on winning the Presidency. Thank you!”
He added, “Interesting how the U.S. sells Taiwan billions of dollars of military equipment but I should not accept a congratulatory call.”
On Sunday, he took another aim at China in his tweets, "Did China ask us if it was OK to devalue their currency (making it hard for our companies to compete), heavily tax our products going into their country (the U.S. doesn't tax them) or to