To corroborate a primary source's claim about an event
Explanation:
By checking different sources, you're actually making sure that you have different opinions and points of view about the same subject. Not only that helps with the reliability of the source but it also might reveal quite a few things about the same vent being studied. If 3 secondary sources differ from a primary source, for example, maybe there's something there that needs to be revealed or understood.
The North Atlantic Treaty Organization was created in 1949 by the United States, Canada, and several Western European nations to provide collective security against the Soviet Union. NATO was the first peacetime military alliance the United States entered into outside of the Western Hemisphere.
