For gaining monopoly of oil businesses in the US after he built his own oil refinery
B. Hitler
He was the leader of Nazi Germany. He thought the German race above all other races.
If a country is isolated, it will have to produce everything that it needs: especially food clothes and medicine. It won't be able to specialize, but it will have to focus on satisfying the needs of the people.
If it is not isolated, it can specialize in the things that it can produce the best and fastest, and hope to exchange it for the things that it can't produce.