Prison guards came at 2 a.m. to wake Scannierth Merlo Lacayo, saying it was time to change cells.

But then he saw other political prisoners being moved about and spiffed up. “They were giving everyone new pants, shirts, cutting their hair,” he said.

Then Mr. Merlo saw representatives of the Roman Catholic Church and the Red Cross and realized that the moment he had been awaiting for 14 months had finally arrived: He and dozens of other political prisoners in Nicaragua were being freed after months of international clamor.

Their sudden release on Monday came after the United States government strengthened sanctions against the authoritarian government of Daniel Ortega, tightening a financial noose around a regime that has been condemned around the world for its crackdown on dissent.

“I had been sentenced to five years for supposedly stealing a Sandinista Party member’s I.D. card, but the real reason was because I was against the government — and I am going to continue to be against the government,” Mr. Merlo said in a telephone interview shortly after his release.