Complex sentence: Despite high heat, rains, and difficult terrain, Scott won the battles of Cerro Gordo, Contreras/Padierna, Churubusco, and Molino del Rey, then assaulted the fort of Chapultepec on September 13,1847, after which the city surrendered.
Split into simpler sentences: Despite high heat, rains, and difficult terrain, Scott won the battles of Cerro Gordo, Contreras/Padierna, Churubusco, and Molino del Rey. He then assaulted the fort of Chapultepec on September 13,1847, after which the city surrendered.