Key point: Washington has wanted to expand NATO's anti-missile capabilities for a while now.
A key NATO missile-defense site in Romania on Aug. 9, 2019 completed a three-month upgrade process that had forced operators to take the system offline.
To fill the resulting gap in coverage, the U.S. Army in May 2019 deployed to Romania one of its seven Terminal High-Altitude Area-Defense missile-interceptor batteries.
The THAAD deployment was controversial.
The THAAD system set up within sight of the Aegis Ashore site in Romania. The Army and the U.S. Defense Department separately posted, then quickly deleted, at least one photo of the battery preparing for duty. Some websites preserved the photo.
THAAD antagonized the Russian government, just like Aegis Ashore has done. Russia "can’t understand what tasks the Aegis Ashore system will accomplish in the missile defense area,” Russian deputy foreign minister Sergei Ryabkov said in late April 2019.
The Pentagon and NATO repeatedly tried to explain their reasoning for deploying THAAD. “At the request of NATO, the secretary of defense will deploy a U.S. Army Terminal High Altitude Area Defense system to Romania this summer in support of NATO ballistic-missile defense,” U.S. European Command announced in early April 2019.
“The THAAD, from the 69th Air Defense Artillery Brigade, 32nd Army Air and Missile Defense Command stationed at Fort Hood, Texas, will integrate into the existing NATO BMD architecture during a limited period of scheduled maintenance and updates on the Aegis Ashore missile-defense system in Romania this summer.”
As of early 2019 the Army had acquired around 200 THAAD rockets for its seven batteries and roughly 40 launchers. The U.S. Missile Defense Agency on its website describes THAAD as a “land-based element capable of shooting down a ballistic missile both inside and just outside the atmosphere.”