I'm just quoting from a website
"the factors leading to the downfall of empires of Ghana, Mali, and Songhai
Climate change and struggles with Berber groups in the Sahara led to the downfall of the Ghanaian Kingdom
Later kings followed the patrilineal tradition, where the eldest son succeeds the father. Since there seems to have been no strict tradition, there were many fights over succession. This led to civil wars and was a large part of the reason why the Mali Empire declined.
Like the Mali Empire, the Songhai Empire also suffered from many battles over succession. In Songhai, the brothers of the king often tried to depose him; in turn, some kings tried to protect themselves by killing all their brothers. The last great battle for succession occurred when a great army general challenged a new king. Many men were killed in the battle for control of the country and the Songhai army was weakened. When troops from Morocco invaded to seize control of and revive the trans-Saharan trade in gold, the Songhai Empire could not win and was conquered, making this the last of the great West African empires."
Answer:
Some city states were monarchies ruled by kings or tyrants. Others were oligarchies ruled by a few powerful men on councils. The city of Athens invented the government of democracy and was ruled by the people for many years.
Answer:
The use of the abacus was expanded and refined.
Explanation:
The abacus was invented during the Yuan Dynasty which lasted between 1206AD till 1368AD and then it was expanded and refined by the Ming Dynasty (1368AD-1644AD).
There have been archaeological proof of this as the writings of Tao Zongyi describes in his book that the new servants, unlike the older and more experienced ones were "just like abacus heads" and that they would not move unless they were made to move. This bears credence to the fact that the abacus was already widely used then.
An abacus was used to count numbers.
I believe it was guerrilla warfare.
