Mountains can affect a nation in many ways. In the United States, the Rocky Mountains hindered westward expansion. Before the development of modern forms of travel, mountains made it more difficult for people to move to the west and for our country to grow. It wasn’t until the South Pass was discovered that people could travel through the gaps in the mountains. Even with the knowledge of the South Pass, travel through the Rocky Mountains region was very difficult.
Mountains can also affect how much precipitation a country or region of a country may receive. Regions on the windward side of a mountain tend to get much more precipitation than regions on the leeward side of the mountain.
Mountains can serve as a great barrier to attack. It is very difficult for the military to move through mountainous regions. It was one reason why Switzerland was able to stay out of both World War I and World War II. The mountains made it too difficult to invade Switzerland.