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.
The Korean War After five years of simmering tensions on the Korean peninsula, the Korean War began on June 25, 1950, when the Northern Korean People's Army invaded South Korea in a coordinated general attack at several strategic points along the 38th parallel, the line dividing communist North Korea from the non-communist Republic of Korea in the south.