The Costa Rican Civil War was the bloodiest event in 20th-century Costa Rican history. It lasted for 44 days (from 12 March to 24 April 1948), during which approximately 2,000 people are believed to have died. The conflict was precipitated by the vote of the Costa Rican Legislature, dominated by pro-government representatives, to annul the results of the presidential elections held in February, alleging that the triumph of opposition candidate Otilio Ulate had been achieved by fraud.