Complex sentence: During the Texan War of Secession from Mexico, Fernández Castrillón served as Santa Anna's aide-de-camp, and was noted for his protests against Santa Anna's decision to immediately assault the Alamo.
Split into simpler sentences: During the Texan War of Secession from Mexico, Castrillón served as Santa Anna's aide-de-camp. He often argued against Santa Anna's decision to immediately assault the Alamo.