How was islam able to cross the sahara desert in the 18th century?
a. at the time, the sahara desert was smaller and less harsh than it is today
b. african slaves escaping from there arab owners brought islam home with them
c. a muslim army went south to conquer african kingdoms in ghana and sudan
d. muslim merchants from north africa followed trading routes through the sahara desert

the fact that could also be added to column b is that during world war ii, specifically between the years 1941 and 1945, japan expanded its territory towards the indonesian territory in what was known later as part of the "pacific war". in that time, japan could conquer the philipines, singapore,   borneo, central java, malang, cebu, sumatra and various other islands of the area, therefore expanding its territory for a brief period of time.