<span> The Mexican/American War was an armed conflict between the United States and Mexico that took place in 1846–1848. However, Mexico
refused to accept these as valid, claiming the border was the Nueces
River. U.S. President James Polk endorsed the Rio Grande boundary, which
incited a dispute with Mexico.
The leaders of europe got together and changed the borders of various countries in hope of creating a large number of countries with relatively similar levels of power