Complex sentence: The ship continued her operations in the Caribbean, basing out of New Orleans and patrolling off Cuba, the Dominican Republic, and the Danish West Indies, the latter on patrol protecting American neutrality, until U.S. entry into World War I in April 1917.
Split into simpler sentences: The ship continued her operations in the Caribbean, basing out of New Orleans and patrolling off Cuba, the Dominican Republic, and the Danish West Indies. The patrols of the Danish West Indies was to protect American neutrality prior to U.S. entry into World War I in April 1917.