12. what frenchmen was a valuable ally of
washington during the war?

Marie-Joseph Paul Yves Roch Gilbert du Motier, Marquis de Lafayette which is simply in the United States known as Lafayette who was a french aristocrat and military officer who fought in American Revolutionary War.

Explanation:

the factors that the economies of the muslim empires prosper were:

1- land trade routes-located between three continents  

2- sea trade routes

trade contributed to the spread of muslim empires, and with that islamic culture led to a growing feeling of internationalism resulted in the transfer of technology, science, and other cultural forms.