Simplify the following text for a Grade 9 native English-speaking person.
Original: The revolutionary army decided to strike for independence and marched on to Guanajuato , a major colonial mining center governed by Spaniards and criollos .
Simplified: The revolutionary army decided to fight for independence . They marched on to Guanajuato , which was a major colonial mining center governed by Spaniards and criollos .