The Aztecs had a lot of enemies and when the Spanish conquistadors arrived to Mexico the Aztec enemies were more than happy to help the Spanish destroy the Aztecs.
The period of disorder after the decline of the Roman Empire led to an extended period of disunity during the Middle Ages that was characterized by feudalism.
It's takeover by Alexander the great.
Persia lost the battles of Granicus, Issus and Gaugamela, which led to Alexander's takeover of the Persian Empire.
It's takeover by Alexander the Great.
Invasion by an ambitious Alexander the Great who took over the Empire and turned it into an empire of his own.
Francisco Pizarro. However, the Incan empire was already declining from disease brought by previous Spanish conquistadors.
After the growth of the Ottoman Empire, the state had already reached its pinnacle. This led to the stagnation and decline of the Ottoman Empire, which lasted hundreds of years.
The period of disorder after the decline of the Roman Empire led to an extended period of disunity during the Middle Ages that was characterized by feudalism.
The short answer is: infighting and the plague.
It's takeover by Alexander the great.
The greed for land and money led to decline of Mughal Empire since more taxes were levied on peasant farmers such as the zazia tax on hindus.
Persia lost the battles of Granicus, Issus and Gaugamela, which led to Alexander's takeover of the Persian Empire.
It's takeover by Alexander the Great.
Invasion by an ambitious Alexander the Great who took over the Empire and turned it into an empire of his own.
Leadership dispute, decline in trade hurt the economy, mercenaries hired.
The Gupta empire declined because of bad resourcesand they didn't have any world peace.
One thing that led to the decline of the Aztec Empire was the shortage of skilled farmers. Mistreating the people they conquered. Additionally, the Spanish Conquistadors ripped the empire apart, destroyed the Aztec Army, killed Moctezuma (the Aztec Leader), and colonized the entire region.