The Ozone layer, which mostly lies on the lower portion of the stratosphere.
How Long Did The Vietnam War Last. The Vietnam War is the longest war ever to have taken place in the American history. It lasted for 16 years and it was terrible for the Americans at that time as the Civil Rights campaign was at its peak and so also the Vietnam War and anti war protests.
Length of Vietnam War http://en.wikipedia.org/wiki/Vietnam_War According to wikipedia, it was fought for 11 years against France between 1946-1957 and 18 years against the U.S. between 1957-1975. Exact dates are sketchy.