South Korea was not included within the area subject to American protection , and would be invaded from North Korea less than six months later .
U.S. Secretary of State Dean Acheson delivered his ' Perimeter Speech ' , outlining the boundary of U.S. security guarantees .
South Korea was not included within the area subject to U.S. protection , and would be invaded from North Korea less than six months later .
U.S. Secretary of State Dean Acheson delivered his ' Perimeter Speech ' , outlining the boundary of U.S. security guarantees .