It depends on which era of Jewish history you are talking about.
Internal conflict
the spanish were jelous and destroyed them
The end of communism and the fall of the Berlin Wall-
How much it was unused
They got attacked by Spain Save
The exploitation of the environment that led to the fall of the Kingdom of Kush involved the Kushites cutting down too many trees on their land. This led to soil erosion and the Kushites were no longer able to farm.
It was a peasants revolt.
There was a weakening of the Mesopotamian and Egyptian states that corresponded with an increasing federalization of the Israelite Tribal confederacy.
The continued guerilla warfare in Spain and the major loss in Russia.
"Around 920 B.C., according to the biblical account, Jeroboam led the revolt of the northern tribes, and established the Kingdom of Israel (1 Kings 11-14). "see link "History of Ancient Israel and Judah" below
ANSWER The French-Prussian War who led to the fall of Napoleon the Third and the rise of The German Empire.
A constant change of rulers, civil wars, and the collapse of the economy due to military spending. This cycle led to a weak, impoverished central government that quietly collapsed in 476.