The 2017–2018 North Korea crisis was a period of heightened tension between North Korea and the United States throughout 2017. The crisis began early in 2017 when North Korea conducted a series of missile and nuclear tests that demonstrated the country's ability to launch ballistic missiles beyond its immediate region, suggesting their nuclear weapons capability was developing at a faster rate than had been assessed by U.S. intelligence. Both countries started exchanging increasingly heated rhetoric, including nuclear threats and personal attacks between the two leaders, which, compounded by a joint U.S.–South Korea military exercise undertaken in August and North Korea's sixth nuclear test in September, raised international tensions in the region and beyond and stoked fears about a possible nuclear conflict between the two nations. In addition, North Korea also threatened Australia twice with nuclear strikes throughout the year for their allegiance with the United States. International relations lecturer and former government strategist Van Jackson said in the book On the Brink: Trump, Kim, and the Threat of Nuclear War that it was the closest the world had come to nuclear war since the Cuban Missile Crisis.

The bilateral relations between the People's Republic of China (PRC) and the Democratic People's Republic of Korea (DPRK) have been generally friendly, although they have been somewhat strained in recent years because of North Korea's nuclear program. They have a close special relationship and China is often considered to be North Korea's closest ally. China and North Korea have a mutual aid and co-operation treaty, signed in 1961, which is currently the only defense treaty either country has with any nation.