Mr. Trump labored for hours on the wording in the address, which was widely praised as one of his most ideologically coherent by the conservative press, on the flight over with his chief speechwriter, Stephen Miller, and his national security adviser, Lt. Gen. H. R. McMaster.

General McMaster dealt with the fine print of security issues, and helped draft language challenging Russia to stop its “destabilizing” behavior in Ukraine and elsewhere. Mr. Miller, an architect of the president’s controversial travel ban, saw Poland, with its large population of religious conservatives and center-right government, as an extension of Mr. Trump’s base back home. The speech he wrote with the president had the sledgehammer directness of a Trump campaign address.

It was the president himself who inserted the element of defiance, dictating the line “The West will never be broken!” to Mr. Miller, according to a senior White House official involved in the process.