There's no such thing as "its own devices" for a country with no surviving government. All the various countries conquered by the Axis during World War II were occupied by various Allied powers with the intention of reestablishing them as independent countries. Poland and Czechoslovakia, to name two, were occupied solely by the Soviets and was set up as Soviet-controlled puppet states. Japan. to name another, was occupied solely by the United States and was reformed into a fairly pro-Western democratic country, complete with baseball.
Some countries were split into occupation zones between the Western allies and the Soviets. Germany was one. There were four occupation zones: British, American, French, and Soviet. The intention was for a new German government to be formed that would govern all four zones, but negotiations broke down and the Soviet occupied zone formed one government (German Democratic Republic, known as East Germany) and the Western occupied zones formed another (Federal Republic of Germany). This state of affairs continued until the fall of communism, when the East Germans more or less decided to join the Federal Republic giving us today's Germany.
Korea was a similar case. There was no Korean government--it was a Japanese possession since 1910--so, with the intent of punishing Japan and giving the Korean people self-determination, it was temporarily occupied by the Allies until they could set up a democratic government. It was partitioned between the Soviets and the Americans, who, as in Germany, formed opposing governments. And then the North invaded the South--and that's where the war began.