Complex sentence: In April 1899 "Montgomery" transferred to the South Atlantic Squadron and operated along the Atlantic coast of South America until returning to the United States and decommissioning at New York City 15 September 1900.
Split into simpler sentences: In April 1899 "Montgomery" transferred to the South Atlantic Squadron and operated along the Atlantic coast of South America. She returning to the United States and decommissioning at New York City 15 September 1900.