What major conflict occurred between 1846 and 1848 during James Polk's presidency?

The major conflict that occurred between 1846 and 1848 during James Polk's presidency is the Mexican-American War. This war was primarily driven by the territorial expansionist policies under Polk, who was a proponent of Manifest Destiny, the belief that the United States was destined to expand across the North American continent. Tensions between the United States and Mexico escalated following the annexation of Texas, which Mexico still considered part of its territory despite Texas declaring independence in 1836.

The conflict officially began when U.S. forces were ordered to advance into the disputed territory between the Nueces River and the Rio Grande, leading to clashes with Mexican troops. The war resulted in significant territorial gains for the United States, including present-day California, Nevada, Utah, Arizona, and New Mexico, as formalized in the Treaty of Guadalupe Hidalgo in 1848.

In contrast, the Civil War occurred much later, from 1861 to 1865, and involved a different set of political and social issues related to slavery and states' rights. The Spanish-American War took place in 1898 and involved conflicts primarily in the Caribbean and the Philippines. The War of 1812 happened between 1812 and 1815, centered around maritime issues