Complex sentence: For months the sea trade routes have been raided by pirates, but their latest success stirs great political unrest, for the princess of Ierendi has disappeared on her sea voyage on one of the Guild's ships.
Split into simpler sentences: For months the sea trade routes have been raided by pirates. However their latest success stirs great political unrest, for the princess of Ierendi has disappeared on her sea voyage on one of the Guild's ships.