North Korea, which is scheduled within days to launch a long-range rocket, has been developing missiles for decades both for what it terms self-defense and as a lucrative export commodity.
It says its upcoming launch, sometime between April 12-16, will put a peaceful satellite in orbit.
The United States and its allies have condemned what they see as a disguised test of ballistic missile technology in defiance of U.N. resolutions.
The North began its program in the late 1970s or early 1980s, when it started working on a version of the Soviet Scud-B with a range of 300 kilometers.
Between 1987 and 1992 it began developing a variant of the Scud-C (range 500 km), as well as the Rodong-1 (1,300 km), the Taepodong-1 (2,500 km), the Musudan-1 (3,000 km) and the Taepodong-2 (6,700 km).
The Scud-B, Scud-C and Rodong-1 have all been tested successfully.
The first and only Taepodong-1 launch took place in August 1998 over Japan.
It sparked alarm in Tokyo but the third stage apparently exploded before it could place a small satellite into orbit.
In September 1999, amid improving relations with the United States, North Korea declared a moratorium on long-range missile testing. It ended this in March 2005, blaming Washington’s “hostile” policy.
The Taepodong-2 was first fired on July 5, 2006 but blew up after 40 seconds.
On April 5, 2009, the North fired a long-range rocket dubbed Unha-2 (Galaxy-2) ― an advanced three-stage variant of the Taepodong-2 ― to put a satellite into orbit.
Experts said the third stage may have separated from the second but apparently failed to ignite.
Japanese reports said the second stage splashed down in the Pacific 3,200 km from the launch site, and the third stage plus satellite fell nearby.
Unha-2 is 30 meters tall and weighs 80-85 tons, according to a 2009 analysis by scientists David Wright and Theodore Postol.
Writing in the Bulletin of the Atomic Scientists, they termed it a “significant advance” on previous launchers and said a modified version could reach the continental United States.
They said the third stage had a strong similarity to Iran’s Safir-2 rocket, suggesting collaboration between the two countries.
Little is known about the Unha-3, scheduled to blast off from a new site in the far northwest, but it is likely to be largely similar to the Unha-2.
The North is thought to have enough plutonium for six to eight small bombs.
But it is unclear whether it has mastered the technology to build a nuclear warhead.
It is thought to have sold hundreds of ballistic missiles to Iran, Iraq, Syria, Pakistan and other countries over the previous decade to earn foreign currency, according to a U.S. Congressional Research Service report in 2007.
