Any member of the fire or police department, who resigned or obtained leave of absence therefrom to serve in the United States air force or air force reserve, army, navy or marine reserve, or marine corps, of the United States, or as a member of the United States army and navy reserve, the Spanish-American War, in the World War 1917-1918, or in World War II from December 7, 1941, to December 31, 1946, both dates inclusive, or in the Korean Conflict at any time between June 25, 1950, and January 31, 1955, both dates inclusive, or in the Vietnam Conflict at any time between August 5, 1964, and ending on the date the armed forces of the United States are directed by formal order of the government of the United States to cease hostilities, both dates inclusive, and has returned with an honorable discharge from such service, to the fire or police department, shall have the period of such service included as part of the member’s period of service in the department.