 In its 10-centuries expansion, Roman civilization shifted from a small monarchy (753 – 509 BC), to a republic (509 – 27 BC), to an autocratic empire (27 BC – AD 476).It came to dominate Western, Central and Southeastern Europe and the entire area surrounding the Mediterranean Sea through conquest using the Roman legions and then through cultural assimilation by eventually giving Roman citizenship privileges to the whole population.Nonetheless, despite its great legacy, a number of factors led to the eventual decline and fall of the Roman Empire.