Seoul: A month after shocking the world with its fourth nuclear test, North Korea has followed through with its plans to fire a long-range rocket, defying outside governments that see the launch as a banned test of ballistic missile technology.
Each nuclear test and long-range rocket launch brings the North closer to creating a nuclear warhead small enough to fit on a missile that could strike the mainland United States.
A look at some key developments in North Korea's nuclear weapons and long-range missile programs:
Feb. 7, 2016: North Korea launches a long-range rocket.
Feb. 6. 2016: North Korea moves the rocket's launch window to Feb. 7-14.
Jan. 6, 2016: North Korea conducts its fourth nuclear test and claims it successfully tested a "miniaturised" hydrogen bomb. Many outsiders are skeptical.
Feb. 13, 2013: North Korea conducts its third nuclear test.
Dec. 12, 2012: North Korea launches a long-range rocket carrying a satellite. The US North American Aerospace Defense Command says the North appears to have put an object into space.
April 13, 2012: North Korea launches a long-range rocket that fizzles shortly after liftoff. North Korea says it failed to deliver a satellite into orbit. The US announces it will not carry out the food aid deal.
Feb. 29, 2012: North Korea announces a moratorium on nuclear and long-range missile tests in food aid deal with the US.
May 11, 2010: North Korea claims to have succeeded in nuclear fusion reaction, leading to speculation that the country was attempting to build a more powerful bomb. Outside experts doubt the North's claim.
June 13, 2009: North Korea says it will start enriching uranium in addition to its plutonium-based program.
Feb. 15, 2009: North Korea claims it has the right to "space development.”
April 14, 2009: North Korea quits six-party nuclear disarmament talks and vows to restart nuclear facilities in protest against international condemnation over its rocket launch.
April 5, 2009: North Korea launches a long-range rocket said to be carrying a satellite. The North claims success, but US North American Aerospace Defense Command says no satellite reaches orbit.
May 25, 2009: North Korea conducts its second nuclear test.
Oct. 11, 2008: US removes North Korea from list of states that sponsor terrorism after the North, which had stopped disablement moves to its plutonium plant, agrees to resume disablement and allow access of US inspectors.
July 14, 2007: North Korea shuts down its main Nyongbyon reactor, later starts disabling it.
Feb. 13, 2007: North Korea agrees to disable its main nuclear facilities in return for energy aid and other benefits.
July 5, 2006: North Korea fires a three-stage rocket with a potential range of 6,700 kilometers (4,100 miles), but it fizzles after liftoff, according to South Korean and US officials. North Korea has never acknowledged the launch.
Oct. 9, 2006: After citing "extreme" threats of a US nuclear attack, North Korea detonates a nuclear device for the first time.
Oct. 15, 2006: UN Security Council adopts a resolution condemning the test, imposing sanctions and banning North Korea from activities related to its nuclear weapons program, including "their means of delivery and related materials."
Aug. 31, 1998: North Korea launches a multistage rocket over Japan and into the Pacific Ocean. Outside experts estimate the rocket's range at 1,550 miles (2,500 kilometers).
