Early this week, shortly after Nicolás Maduro held a sham referendum on whether Venezuela should annex the majority of neighboring Guyana, Presdient Biden’s top national security advisers ordered a classified assessment of Venezuelan troop movements on and around the border, a U.S. defense official said. Maduro seemed to be acting on what had initially been viewed in Washington as a domestic political ploy. He would soon establish a combatant command to oversee the territory, known as Guayana Esequiba, and the White House wanted to know how serious he was. Multiple U.S. officials tell McClatch…