Timeline:
August 2013: North Korea reported to have restarted nuclear reactor to produce plutonium
May 2015: North Korea claims to have tested a submarine-launched missile; says it developed technology to mount nuclear warhead on a missile
July 2014: North Korea conducts series of missile tests ahead of Chinese President Xi Jinping’s visit to Seoul
September 2015: North Korea threatens nuclear attack against U.S. and reaffirms its main reactor is operational. South Korean President Park Geun-hye says North will “pay a price” for fourth test
December 2015: Kim Jong Un says North Korea is “ready to detonate” a hydrogen bomb
Jan. 6, 2016: North Korea says it successfully tests hydrogen bomb
Feb. 7, 2016: North Korea launches a long-range rocket that it says successfully put a satellite into orbit
Aug. 24, 2016: North Korea successfully launches a ballistic missile from a submarine
Sept. 5, 2016: North Korea fires three ballistic missiles about 1,000 kilometers, at least one of which entered Japan’s air defense zone
Sept. 9, 2016: North Korea conducts fifth nuclear test
Oct. 16, 2016: North Korea fires a ballistic missile that immediately explodes after launch
Feb. 12, 2017: North Korea fires an intermediate-range Pukguksong-2 ballistic missile into nearby seas, drawing a joint rebuke from Trump and Japanese Prime Minister Shinzo Abe, who were meeting in Florida
March 6, 2017: North Korea fires four ballistic missiles, with three falling into Japan’s exclusive economic zone
April 16, 2017: North Korea fired an unidentified ballistic missile that exploded almost immediately after launch, defying warnings from the Trump administration to avoid any further provocations
https://www.bloomberg.com/politics/articles/2017-04-16/north-korea-missile-launches-nuclear-detonations-timeline