Complex sentence: Toward the end of the war Lycophron established a tyranny at Pherae and on his death Jason became dictator and by around 374 B.C.E. extended his rule throughout Thessaly.
Split into simpler sentences: Toward the end of the war Lycophron established a tyranny at Pherae. On his death his son Jason became dictator and by around 374 B.C.E. extended his rule throughout Thessaly.