Complex sentence: In early 1912, the United States government sent a detachment of 688 US Marines, officers and enlisted men, to Guantanamo Naval Base, while, Estenoz and his followers were preparing an armed rebellion.
Split into simpler sentences: In early 1912, the United States government sent a detachment of 688 officers and enlisted US Marines to Guantanamo Naval Base. Meanwhile, Estenoz and his followers were preparing an armed rebellion.