Which was one of Spain's main
economic forces under Phillip II?

Philip was forced heavily to rely on taxes in Spain and in 1561 the servicio tax was made a regular one, the excusado was introduced in 1567 and the crusada tax, together were known as the “Three Graces” reaching as much as 1.4 million ducats per year in the 1590's.

Explanation:

descendants of muhammed