Final answer:
The Capture of Mexico City in September 1847 during the Mexican-American War convinced many Mexicans that they could not win against the United States. This event led to the ultimate fall of Mexico and the signing of the Treaty of Guadalupe Hidalgo, ceding significant territories to the U.S. and heightening the spirit of Manifest Destiny.
Step-by-step explanation:
The timeline presented, consisting of the Battle of Palo Alto, the Battle of Monterrey, the Battle of Buena Vista, and the Capture of Mexico City, relates to the major events of the Mexican-American War. The event that likely convinced many Mexicans that they could not win the war was the Capture of Mexico City.
This turning point marked a significant military success for the United States, as American forces captured the capital of Mexico in September 1847. General Winfield Scott's campaign culminated with the fall of Mexico City, a symbolic and strategic victory that effectively ended the war. Following this defeat, Mexican resistance crumbled, and the war concluded with the Treaty of Guadalupe Hidalgo. The treaty had Mexico cede a vast portion of territory, including present-day California, Arizona, New Mexico, Nevada, Colorado, Utah, and parts of Wyoming, to the U.S., which had tangible implications on the notions of Manifest Destiny.
The capture of the Mexican capital reinforced the perception that Mexico could not militarily withstand the United States' expansionist drives. Moreover, the socio-political effects of the war influenced the domestic politics surrounding slavery, with tensions flaring into what would eventually become a sectional crisis within the United States. The Peace of Guadalupe Hidalgo institutionalized the territorial losses for Mexico, further endorsing the long-term sentiment of defeat.