The Pentagon confirmed today that the US military will deploy a THAAD ballistic missile defence system to Guam.
THAAD, which stands for Terminal High-Altitude Air Defence, is a system that shoots down short and medium range missiles.
It is considered one of the last lines of defence against an incoming threat, does not carry an explosive warhead and travels over twice the speed of a bullet.
Watch the video below to find out more about THAAD.
Through her tears, a North Korean woman told me how she had to escape: risk death while running across the border or die of starvation.
Memories of the Korean war are never far away in South Korea, where residents have grown used to living with the constant threat of war.
North Korea said it will withdraw workers from the Kaesong factory park run jointly with South Korea and suspend all operations there.