The Declaration of Independence of the United States eloquently states in its introductory paragraph: "When in the course of human events it becomes necessary for one People to dissolve the political bands which have connected them with another.... a decent respect for the opinions of mankind requires that they should declare the causes which impel them to the separation".
These words are also appropriately to describe the great event in Mexican history of Mexico's Independence from Spain. This occurred not on "Cinco de Mayo" (May 5th, 1862), but on September 16th, 1810. Mexico celebrates the Fifth of May to commemorate the victory of the Mexican army over the occupying army of France at Puebla in May of 1862. The victorious Mexican general Ignacio Zaragoza, was born in Goliad, Texas, and his shared Texan Mexican heritage inspires celebration in both lands.
The celebration of Mexican independence, however, dates back even further, to 1810. Mexico was known officially as "La Nueva España," (New Spain) the most important Spanish colony in the New World. Its supreme ruler was King Ferdinand VII of Spain, whose representative in Mexico was the "Virrey" (Viceroy). The military ambitions of Napoleon Bonaparte had severely disrupted the political situation in Europe and in the Spanish Empire. Napoleon's revolutionary upheaval also posed a very real threat to the cherished treasures of the people of New Spain: a highly developed culture of almost three centuries and the Catholic religion.
The Napoleonic threat to Mexican culture united two mayor groups in New Spain: the "criollos"; the descendents of Spainards born in Mexico, and the "mestizos"; the descendents of mixed marriages between Spaniards and native peoples. To protect these cherished values, "Los Insurgentes," a movement to make Mexico a sovereign nation, arose in Queretaro. One of the leaders of the movement was Miguel Hidalgo y Costilla, the pastor of the nearby parish of Dolores. When he learned on September 15th, 1810, that the Queretaro conspiracy had been discovered by the Spanish authorities, he had no choice but to begin the rebellion.
http://www.mexconnect.com/MEX/austin/grito0996.html