structural:scholar_edition, structural:reformatting
Cold War (1947–1991)

During the Cold War, a new definition emerged. Earth was divided into three "worlds". The First World, analogous in this context to what was called the West, was composed of NATO members and other countries aligned with the United States.

The Second World was the Eastern bloc in the Soviet sphere of influence, including the Soviet Union (15 republics including the then-occupied and presently independent Estonia, Latvia, Lithuania) and Warsaw Pact countries like Poland, Bulgaria, Hungary, Romania, East Germany (now united with Germany), and Czechoslovakia (now split into the Czech Republic and Slovakia).

The Third World consisted of countries, many of which were unaligned with either, and important members included India, Yugoslavia, Finland (Finlandization) and Switzerland (Swiss Neutrality); some include the People's Republic of China, though this is disputed, since the People's Republic of China, as communist, had friendly relations—at certain times—with the Soviet bloc, and had a significant degree of importance in global geopolitics. Some Third World countries aligned themselves with either the US-led West or the Soviet-led Eastern bloc.

A number of countries did not fit comfortably into this neat definition of partition, including Switzerland, Sweden, Austria, and Ireland, which chose to be neutral. Finland was under the Soviet Union's military sphere of influence (see FCMA treaty) but remained neutral and was not communist, nor was it a member of the Warsaw Pact or Comecon but a member of the EFTA since 1986, and was west of the Iron Curtain. In 1955, when Austria again became a fully independent republic, it did so under the condition that it remain neutral; but as a country to the west of the Iron Curtain, it was in the United States' sphere of influence. Spain did not join the NATO until 1982, seven years after the death of the authoritarian Franco.

The 1980s advent of Mikhail Gorbachev led to the end of the Cold War following the dissolution of the Soviet Union.