Soldiers from the fort saw action when Confederate Army raiders entered Portland Harbor on June 26, 1863, aboard a captured ship named "Archer". The Confederates captured the United States Revenue Cutter "Caleb Cushing" the next day, and attempted an escape in an action known as the Battle of Portland Harbor. They were pursued by two steamers carrying soldiers and artillery pieces from Fort Preble, as well as about 100 civilian volunteers. Light wind made escape impossible and the Confederates abandoned the "Caleb Cushing" in boats after setting the ship on fire. The fire detonated the ship's magazines and the "Cushing" was destroyed by the explosion. Twenty-three Confederate prisoners were captured and taken to Fort Preble. They remained at Fort Preble until they were transferred to prisoner of war camps.