When Chinese leader Xi Jinping inserted a reference to “twists and turns” in his relationship with President Donald Trump in the opening remarks of their summit this week, he could hardly have imagined the twist that came minutes before the talks began.

Writing from Marine One, which was gliding toward the airport in South Korea where he was due to meet Xi, Trump instructed the Pentagon to resume nuclear testing after a 33-year pause, citing other nations’ — including China’s — own capabilities.

“That process will begin immediately,” the president wrote on social media.

The directive took even many of Trump’s advisers off guard, according to officials, leading to unanswered questions about when, or if, the testing would actually begin. Historically, it is the Department of Energy that maintains and tests the US nuclear stockpile, not the Department of Defense. And engineers have said accurate tests can be conducted through computer simulation, not blowing up an actual warhead underwater or in the Nevada desert.

Hours after the president’s post, it did not appear as if the Pentagon was moving swiftly to test a nuclear weapon. Testifying on Capitol Hill, the senior military officer nominated to oversee the American nuclear arsenal said Thursday morning he was not “reading anything” into Trump’s Truth Social post — an indication,