Defense Department leaders, including Undersecretary of Defense for Policy John C. Rood and Air Force Gen. Terrence J. O’Shaughnessy, commander of North American Aerospace Defense Command and U.S. Northern Command; appeared before a hearing of the Senate Armed Services Committee’s strategic forces subcommittee to discuss the nation’s missile defense policies and programs.

Missile defense involves detecting, tracking, intercepting and destroying enemy missiles. The United States uses three types of missile defense, often referred to as a layered defense posture:

• • Tactical, short-range tactical ballistic missiles with a range of about 50 miles
  • Theater medium-range missiles that range up to about 200 miles
  • Strategic, long-range, intercontinental ballistic missiles that can travel wherever needed on Earth.

The missile defense architecture also comprises three components:

• • Networked sensors, including space- ground- and sea-based radars for target detection and tracking
  • Ground- and sea-based interceptor missiles for destroying ballistic missiles using either the force of a direct collision, called “hit-to-kill” technology, or an explosive blast fragmentation warhead
  • A command, control, battle management and communications network providing operational commanders with links between the sensors and interceptor missiles

Partnerships are an integral part of missile defense, Pentagon officials said, noting that the United States has missile defense cooperative programs with a number of allies, including the United Kingdom, Japan, Australia, Israel, Denmark, Germany, the Netherlands, the Czech Republic, Poland, Italy and many others.