MOSCOW — It began with a state visit by senior Russian officials to a separatist enclave in another country. It ended with Russia threatening economic retribution against several European nations on Monday, after the plane carrying the delegation was grounded in Moldova and raided by the local police.

Emerging as a central figure in the diplomatic drama was Dmitri O. Rogozin, the Russian deputy prime minister who led the trip and was on the list of those hit with sanctions by both the United States and European Union after Russia’s annexation of Crimea in March.

An unapologetic nationalist, he is best known to users of social networks for his shows of defiant and undiplomatic bravado.

“Crimea is ours. Basta,” Mr. Rogozin said on Twitter, using the Italian word for “enough,” during a visit to the Crimean Peninsula in late March as tensions soared between Russia and the United States.