Oil is an essential lubricant in your engine. It lets metal press against metal without damage. For example, it lubricates the pistons as they move up and down in the cylinders.
1 By the time of the Japanese surrender in August 1945, Korea was the second-most industrialized nation in Asia after Japan itself.  But the wartime mobilization of 1937-45 had reintroduced harsh measures to Japanese colonial rule, as Koreans were forced to work in Japanese factories and were sent as soldiers to the front.
In 1950 the Korea Peninsula was divided between a Soviet-backed government in the north and an American-backed government in the south. The division of Korea into two halves had come at the end of World War II. In August of 1945 the Soviet Union invaded Korea, which had been under Japan's control since 1910.