Complex sentence: Despite Portugal's nominal claims, as late as the 19th century, their control over the interior country of Angola was minimal, but the 16th century saw them gain control of the coast through a series of treaties and wars.
Split into simpler sentences: Despite Portugal's nominal claims, as late as the 19th century, their control over the interior country of Angola was minimal. In the 16th century Portugal gained control of the coast through a series of treaties and wars.