U.S Pacific Command in Hawaii has deployed the "first elements" of a ballistic missile defense system to South Korea.
The action comes after North Korea launched multiple missiles over the weekend, in a provocative move that drew immediate condemnation.
The Terminal High Altitude Area Defense system is described as being part of a layered missile defense system.
Military officials decided in July 2016 to send the THAAD to South Korea as part of an alliance with the country. The system intercepts and destroys short- and medium-range ballistic missiles inside or outside the atmosphere.
"We will resolutely honor our alliance commitments to South Korea and stand ready to defend ourselves, the American homeland and our allies," said Adm. Harry Harris, commander of U.S. Pacific Command, in a news release.