The invasion of Poland by led to France and Britain declaring war on the aggressor nation. This is commonly considered the official start of World War II.

Germany and Soviet Union
(They did not declare war on the Soviet Union though)

The mountain men With the silk trade and quick collapse of the North American beaver-based fur trade in the later 1830s–1840s, many of the mountain men settled into jobs as Army Scouts, wagon train guides, and settlers through the lands which they had helped open up.