Complex sentence: His discovery of extensive deposits of saltpeter in the region led to the company expanding into the region, which at the time was contested with Bolivia, and began mining in the region with the intent of shipping nitrates to the company's British partners.
Split into simpler sentences: His discovery of extensive deposits of saltpeter led to the company expanding into the region, which at the time was contested with Bolivia. The company began mining in the region with the intent of shipping nitrates to the company's British partners.