Conversation so far:
when was the second world war took place
World War 2 happened 1 September 1939 – 2 September 1945.
how long was ww2
World War 2 was 6 years and 1 day.
who won ww2
WWII was an Allied Victory.
did many people died in ww2
World War II was the deadliest conflict in human history, marked by 70 to 85 million fatalities, most of whom were civilians in the Soviet Union and China.

Question: what was unique about the war
Self-contained rewrite: what was unique about the ww2