The Roman, Han, Persian, Mauryan, and Gupta empires all experienced declines due to similar factors: 1) Excessive demands on resources caused environmental damage and social tensions as wealth concentrated among elites. 2) External security problems along frontiers, including invasions, threatened the empires. 3) The Gupta Empire was overrun by the White Huns in the 5th century AD, contributing to its decline, while the Roman Empire disintegrated under invasions and lost its western half by 476 AD.