Complex sentence: Before the close of World War I, "Denver" made eight such voyages, then was detached on 5 December 1918 to patrol the east coast of South America, returning to New York on 4 June 1919.
Split into simpler sentences: Before the close of World War I, "Denver" made eight such voyages. Following the Armistice, "Denver" was detached on 5 December 1918 to patrol the east coast of South America, returning to New York on 4 June 1919.