An opposition demonstrator wears a gas mask against tear gas during clashes with security forces in a protest against the government of President Nicolas Maduro on the anniversary of the 1958 uprising that overthrew the military dictatorship, in Caracas on January 23, 2019. - Venezuela's National Assembly head Juan Guaido declared himself the country's "acting president" on Wednesday during a mass opposition rally against leader Nicolas Maduro. (Photo by Federico Parra / AFP)