The United States announced it is sending an advanced anti-missile system and a number of troops to Israel, deepening America’s involvement in the spiraling conflict as the region readies for Israeli retaliatory strikes against Iran.

The decision was announced just hours before a Hezbollah drone strike on an Israeli base killed four soldiers and wounded 61 others without triggering an alert.

The Terminal High Altitude Area Defense, known as THAAD, usually requires about 100 troops to…