Conversation so far:
what was the effect of the iron curtain
The Iron Curtain greatly impacted the geographic, political, and economic landscape of Europe starting in 1945 and extending to the modern day.
where did the term iron curtain originate
The term Iron Curtain as a metaphor for strict separation goes back at least as far as the early 19th century. It originally referred to fireproof curtains in theaters.
how long was the physical barrier of the iron curtain
The Iron Curtain later became a term for the 7,000 kilometre long physical barrier of fences, walls, minefields, and watchtowers that divided the east and west.
what were the countries to the east of the iron curtain
The nations to the east of the Iron Curtain were Poland, East Germany, Czechoslovakia, Hungary, Romania, Bulgaria, Albania, and the USSR.

Question: what were the countries that made up the union
Self-contained rewrite: what were the countries that made up the soviet union