Testimony has emerged revealing that just days before U.S. President Donald Trump announced a reciprocal tariff policy that shook the world in April of last year, the specific tariff rates had not even been finalized.

According to the new book "Regime Change," written by New York Times White House correspondents, the White House at the time was in a state of extreme chaos, driven by President Trump’s personal intuition and stubbornness rather than thorough simulation.

Ahead of the policy announcement, the U.S. Secretary of Commerce and the Secretary of the Treasury had sent warnings to officials in other countries, telling them "not to take retaliatory measures." However, because they did not know what decision President Trump would ultimately make, the content of these warnings was inevitably vague.

The authors of the book recount an anecdote from a meeting on March 26 of last year, one week before the tariff policy was announced. When the Secretary of Commerce presented data on tariff rates against the U.S. calculated by the Office of the United States Trade Representative, President Trump reportedly flew into a rage, calling them "f***ing made-up numbers."

President Trump then ordered another aide, "Just Google it. And bring me the real numbers."

This was based on his personal hunch that the tariff rates imposed on the U.S. by countries like China or India were much higher than official statistics suggested.

In the end, the reciprocal tariff rates for each country were determined in a haphazard manner in consultation with Peter Navarro, an advisor often referred to as the "tariff strategist."

An arbitrary formula was used, which involved taking the trade deficit, dividing it by the import amount, and then halving that figure. The Secretary of Commerce reportedly even expressed self-deprecating frustration about this to his close associates.

When media criticism poured in the day after the announcement, President Trump shifted the blame in private, saying, "It’s because of Navarro’s stupid numbers."

In the aftermath of this haphazard tariff policy, the financial markets were hit hard, with the S&P 500 index plunging 12% over two days and government bond yields soaring.

Nevertheless, President Trump attempted to maintain the irrationally high tariff rates for even longer.

The authors report that Secretary of the Treasury Mnuchin compared this extreme risk-taking tendency of Trump to George Soros, the godfather of hedge funds, in private, evaluating it as a key factor in President Trump's political success.

Reported by Lee Hyeon-yeong | Video by Choi Gang-san | Graphics by Yook Do-hyun | Produced by SBS Digital News