As a NATO summit he threw into chaos wrapped up Thursday, President Donald Trump cheekily declared himself a “very stable genius.”

The other world leaders present mostly begged to differ.

Trump’s wildly unpredictable performance over two days in Brussels left many European leaders convinced that there is little method to the American president’s rhetorical madness, and simply no way to anticipate what he might do next.

“Nobody knows when Trump is doing international diplomacy and when he is doing election campaigning in Montana,” Danish defense minister Claus Hjort Frederiksen said. “It is difficult to decode what policy the American president is promoting. There is a complete unpredictability in this, and one of the things you need in this alliance is predictability towards Russia.”

Frederiksen said NATO allies now “live with the uncertainty” that Trump “plays in a completely different way than the rest of us.”