The Seven Years’ War (1756–1763) formed the background for independence movements in the Americas. Great Britain increased its colonial land and was forced to make reforms in order to govern its territory, as was Spain, in order to modernize. Their subjects felt the consequences. Because of their experience in politics, those from the Thirteen Colonies resisted and eventually declared independence in 1776. France had been weakened by its losses and recognized the Confederation in 1778, before drawing Spain into the short fight. Because they were less important than their territory in the West Indies, Great Britain recognized their independence in 1783, ceding them the territory up to the Mississippi. The French Revolution allowed them to strengthen their government, trade as a neutral country, and purchase Louisiana in 1803.
New Spain was unfortunate in that it was a valuable viceroyalty of Spain, and, as it did not have allies, its long and bloody fight broke apart the administration. Upon achieving independence in 1821, it found itself in a deplorable situation. Impoverished and without political experience, it aroused the ambition of new trade countries and of the United States, the uninhabited territory to its north. To populate it, Mexico offered facilities and attracted American settlers, who violated the conditions that had been set and declared independence in Texas, joining the United States in 1845.
Mexico’s political inexperience, coupled with the siege coming from Spain, France, and the United States, prevented the country from consolidating a system of government and reviving its economy. By 1840, it exhibited a substantial contrast with the United States, which had a stable government, a connected and productive territory, and a growing population. In 1845, after annexing Texas, population reached nearly 20 million, while Mexico scarcely had 7 million.
By the time the United States initiated the attack, the result was foreseeable. Various armies were invading, and their fleets seized the ports in February 1847. New Mexico and California had been invaded and annexed, and the occupation was a heavy burden, as President Polk forced Mexico to pay. The bitter peace treaty was signed in 1848, and the United States’ newly annexed territory stretched to the Pacific.