How were the rulers of the early West African empires able to control the trans-Saharan trade?

Gold Trade and the Mali Empire Trans-Saharan routes began to bypass Audaghost, expanding instead toward the newly opened Bure goldfield. Soso, the southern chiefdom of the Soninke, gained control of Ghana as well as the Malinke, the latter eventually liberated by Sundiata Keita, who founded the Mali empire.

the treaty of brest-litovsk was a peace treaty signed on 3 march 1918 between the new bolshevik government of russia and the central powers (german empire, austria-hungary, bulgaria, and the ottoman empire), that ended russia's participation in world war i.

no options provided, here,but the answer to this question is often: a historian cites a japanese newspaper article published a year after the end of world war ii in order to draw conclusions about the effect of the war on the japanese economy.

clearly from the answer, the historian alludes to historical sources,and records to aid in analyzing and drawing conclusion on the effect of the war on the economy of japan.