Complex sentence: The U.S. fleet attacking Santiago needed shelter from the summer hurricane season, thus nearby Guantánamo Bay, with its excellent harbour, was chosen for this purpose and attacked on June 6 (1898 invasion of Guantánamo Bay).
Split into simpler sentences: The U.S. fleet attacking Santiago needed shelter from the summer hurricane season. Thus nearby Guantánamo Bay with its excellent harbour was chosen for this purpose and attacked on June 6 (1898 invasion of Guantánamo Bay).