Why?

The Mexican War of Independence (Spanish: Guerra de Independencia de México) was an armed conflict, and the culmination of a political and social process which ended the rule of Spain in the territory of New Spain. The war had its antecedent in the French invasion of Spain in 1808 and extended from the Grito de Dolores on September 16 of 1810, to the entrance of the Army of the Three Guarantees to Mexico City on September 27 of 1821