By Mariana Zuñiga 4-5 minutes Venezuelan opposition leader Juan Guaido speaks with a military member near the Generalisimo Francisco de Miranda Airbase, "La Carlota," in Caracas, Venezuela, April 30, 2019. (REUTERS/Manaure Quintero ) Anthony Faiola Correspondent covering Latin America, Venezuela, Argentina, Brazil, human rights, poverty, globalization and economics April 30 at 7:15 AM CARACAS, Venezuela — Venezuelan opposition leader Juan Guaidó appeared early Tuesday to be staging a military-backed challenge to President Nicolás Maduro, issuing a video with troops that he said was recorded at a base in Caracas and urging other soldiers to join the final stage of “Operation Liberty” meant to force the socialist leader from power. “People of Venezuela, the end of usurpation has arrived,” Guaidó said. “At this moment, I am with the main military units of our armed forces, starting the f