Complex sentence: The Union dispatched a fleet to Hampton Roads to enforce the blockade, and on May 18--19,1861, Federal gunboats based at Fort Monroe exchanged fire with the Confederate batteries at Sewell's Point.
Split into simpler sentences: The Union dispatched a fleet to Hampton Roads to enforce the blockade. On May 18--19,1861, Federal gunboats based at Fort Monroe exchanged fire with the Confederate batteries at Sewell's Point.