What do you consider to be the most important

event of the Cold War? Why?

It was a key Cold War event that begin on October 4 1957 when the Soviet union launch Sputnik 1, the first artificial earth satellite.

It was a key Cold War event that began on October 4, 1957 when the Soviet Union launched Sputnik 1, the first artificial Earth satellite. The launch of Sputnik I rattled the American public.