Last month (May 2019) the United States deployed Terminal High Altitude Area Defense (THAAD) ballistic missile defence batteries to Romania.
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NATO Press Release: At the request of NATO, the United States has deployed a Terminal High Altitude Area Defense (THAAD) battery – a missile defence system built to intercept incoming ballistic missiles – to Romania, to supplement the existing system during maintenance.
THAAD will help provide Ballistic Missile Defence to NATO Allies from Naval Support Facility Deveselu while Aegis Ashore, the primary Ballistic Missile Defence system, undergoes necessary software upgrades. Footage includes shots of the Aegis Ashore Ballistic Missile Defence system and the THAAD batteries, as well as soundbites from US and Romanian officers.