Historically since the 1990’s North Korea has produced one or two nuclear weapons. They also in 1998 fired ballistic missiles over Japan which was treason of the treaty that they had signed prior the years before. Tension was built from the production of the nuclear program and there was fear that a war would break out. The UN learned that North Korea had “crossed the red line” when they found that they had been diverting fuel from Yongbyon.
Another event occurred in 2002 when North Korea said that they would abandon the non-aggression treaty. This caused George Bush to name North Korea as an access of evil and with the help of Japan suspended the fuel oil to North Korea. With that label North Korea was put on the terrorist watch list and more U.S troops were deployed to the DMZ zone. In 2003 the U.S witnessed North Korea moving 8,000 plutonium rods out of storage which is enough to make a lot of Nuclear Weapons. North Korea threatened to test the nuclear weapons.
All of these events lead up to 2007 when North Korea agreed to disclose its nuclear programs and disable all facilities. In return they wanted 950,000 metric tons of fuel oil. The North Koreans wanted to be taken off the terrorism list which the US believed to be a bad idea. George Bush agreed to negotiate the sides on the terms of the treaty they had signed. When the US went in to denuclearize North Korea they found that they had enough plutonium to make half a dozen bombs.