Complex sentence: In 480 BC the Thracians from the south extended their rule over Dobruja and in 339 BC it was conquered by Alexander the Great and brought under Macedonian rule, which was weakened after his death.
Split into simpler sentences: In 480 BC the Thracians from the south extended their rule over Dobruja. In 339 BC it was conquered by Alexander the Great and brought under Macedonian rule, although their control weakened after his death.