Having enrolled prior to World War II as an officer in the reserves, he was made liaison officer between the Commonwealth government and the United States Army Forces in the Far East headquarters of General Douglas MacArthur. He accompanied President Quezon to Corregidor where he supervised the destruction of Philippine currency to prevent its capture by the Japanese. When Quezon left Corregidor, Roxas went to Mindanao to direct the resistance there. It was prior to Quezon's departure that he was made Executive Secretary and designated as successor to the presidency in case Quezon or Vice-President Sergio Osmeña were captured or killed.