-- A U.S. official confirmed today that North Korea has launched a two-stage intercontinental ballistic missile. This is the first successfully test-fired ICBM for North Korea, which has been attempting to build a missile that can reach the U.S. mainland.
The Department of Defense has an extensive missile defense system designed to help protect against a missile attack from that country.
Ground-based midcourse defense system
The ground-based midcourse defense system is designed to counter a North Korean missile threat, including ICBMs, which a minimum range of 3,400 miles. North Korea has stated openly that it wants to develop an ICBM capable of striking the United States mainland with a nuclear weapon.
In May the U.S. conducted the ground-based intercept system's first test against an ICBM-class target. The interceptor was launched from Vandenberg Air Force Base in California, and the ICBM target was launched from Kwajalein Atoll, part of the Marshall Islands in the Pacific. The result: The ICBM was intercepted, which was likened to firing a bullet and hitting another bullet.
"This system is vitally important to the defense of our homeland, and this test demonstrates that we have a capable, credible deterrent against a very real threat," said Vice Adm. Jim Syring, the director of the Missile Defense Agency at the time.
There are 36 ground-based interceptors at two military bases in the U.S. — 32 at Fort Greely in Alaska and four at Vandenberg.
The THAAD system
The THAAD system operates by using hit-to-kill technology and consists of missile batteries coordinated by a radar and tracking system.
A THAAD system was recently deployed in South Korea.
Aegis ballistic missile defense
The Aegis ballistic missile defense is the Navy part of the Missile Defense Agency's defense system. Though not designed to defeat ICBMs, Aegis ballistic missile defense ships can track ICBMs and provide fire control data to the ground-based interceptors in Alaska and California.
Navy destroyers and cruisers equipped with the system carry interceptor missiles capable of targeting an ICBM shortly after launch.
US troops and carriers
The U.S. has 28,500 troops permanently stationed in South Korea and 54,000 troops in Japan.
In Japan the U.S. Navy has stationed destroyers and cruisers capable of destroying missiles launched from North Korea.
The aircraft carrier USS Ronald Reagan, in Yokosuka, Japan, frequently conducts patrols throughout the Pacific. While not a part of the ballistic missile defense system, its presence in the Sea of Japan is meant to deter provocations by North Korea.
The carrier is currently participating in a regional exercise off Australia's east coast.
ABC News' Elizabeth McLaughlin contributed to this report.