Complex sentence: Aguinaldo returned from exile, most of the Philippine revolutionaries rallying to his cause, and negotiated with the Americans, while the Americans in 1898 defeated the Spaniards in what was called a mock battle in Manila, and took control of the city.
Split into simpler sentences: Aguinaldo returned from exile, most of the Filipino revolutionaries sided with him, and negotiated with the Americans. However, the Americans had defeated the Spanish in 1898 in what was called a mock battle in Manila, and took control of the city.