Complex sentence: Since the beginning of Puerto Rico's colonization by Spain in 1508, its inhabitants were Spanish citizens, and it remained Spanish territory despite invasion attempts by the French, Dutch, and the British.
Split into simpler sentences: Since the beginning of Puerto Rico's colonization by Spain in 1508, the inhabitants of Puerto Rico were Spanish citizens. For over 400 years, Puerto Rico remained Spanish territory despite attempts to capture the island by the French, Dutch, and the British.