Complex sentence: There were several external military challenges from Chinese and Japanese pirates, the Dutch, the English and the Portuguese but these were successfully fought-off despite these hostile forces having encircled the Philippine archipelago in a crescent formed from Japan to Indonesia.
Split into simpler sentences: There were several external military challenges from Chinese and Japanese pirates, the Dutch, the English and the Portuguese. Those challengers were fought-off despite the hostile forces having encircled the Philippine archipelago in a crescent formed from Japan to Indonesia.