Complex sentence: The Portuguese reigned supreme from 1500 to 1663 when they lost to the Dutch who remained in power until they surrendered Cochin to the British East India Company in 1795.
Split into simpler sentences: The Portuguese reigned supreme from 1500 to 1663 when they lost to the Dutch. The Dutch were in Cochin until they surrendered Cochin to the (British) East India Company in 1795.