Complex sentence: In August 1829, Spain sent troops from Cuba to invade Tampico in an effort to regain control of the region, but in September, General Antonio López de Santa Anna forced the Spanish troops to surrender, and Mexican control of Tampico was re-established.
Split into simpler sentences: In August 1829, Spain sent a force of troops from Cuba to invade Tampico in an effort to regain control. But, in September General Antonio López de Santa Anna led forces that brought the Spanish troops to surrender, and Mexican control of Tampico was re-established.