Complex sentence: Tondo's regional prominence further culminated during the period of its associated trade and alliance with Brunei's Sultan Bolkiah, and by around 1500 the kingdom reached its peak as a thalassocratic force in the northern part of the archipelago.
Split into simpler sentences: Tondo's regional prominence further culminated during the period of its associated trade and alliance with Brunei's Sultan Bolkiah. And by around 1500, the kingdom reached its peak as a thalassocratic force in the northern part of the archipelago.