The goal of containment (Truman Doctrine) was to box in the Soviet Union to prevent them from effectively spread communism.
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The following issues played the largest role in motivating the events Charles Sumner criticizes in the wrongful declaration of war against México: "The increasing U.S. desire to annex Mexican territories in New
Mexico and California."
Charles Sumner (1811-1874) was a United States Senator from Massachusetts, who opposed slavery in the country. He also was considered to be one of the toughest radical Republicans in Congress who exerted pressure during the American Civil War.
Regarding the imperialistic desires of the United States, he supported the annexation of Alaska, but had his reserves regarding the Mexican territory and opposed the annexation of the Dominican Republic in the Caribbean.
The railroads had a much greater Impact on America than the canals and steamboats, as these allowed you to cross the country much, much quicker. This also allowed food, mainly cattle to be transported, without the flesh rotting. It also had a big Impact on the Native Americans, as this went through a lot of their land.
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