Pope Francis said Tuesday that assassinated Salvadoran Archbishop Oscar Romero––an iconic figure of the bloody civil wars that tore Central America apart and deeply divided the Catholic Church––be declared a martyr, easing his route to eventual sainthood.

The decision by Pope Francis, the Church’s first Latin American pope and a man who personally experienced the terror and bloodshed that tore apart the region as a priest in Argentina during that country’s own “dirty” civil war, recognizes that Archbishop Romero had been...