On 28 July 2015, the Navy tested the modified SM-6 Dual I version to successfully intercept a ballistic missile target in the terminal phase, the last few seconds before it would impact; the Dual I upgrade adds a more powerful processor that runs more sophisticated targeting software to hit a warhead descending from the upper atmosphere at extreme speed. This adds to the fleet's missile defense capabilities by allowing it to intercept ballistic missiles that could not be hit by SM-3 missiles, which targets missiles in the midcourse phase. The Navy had used the SM-2 Block IV as a terminal missile interceptor, but the SM-6 combines missile defense with traditional cruise missile and aircraft interdiction in the same package.