This book shows how North Korea's nuclear programme is central to Kim Jong-un's strategy for survival and leverage, tracing its roots to the origins of the North Korean state and the evolution of its security policies under Kim Jong-il. It analyses how, upon assuming power, Kim rapidly accelerated nuclear weapons development, culminating in advanced missile tests and a declared nuclear deterrent. This programme plays a key role in promoting regime legitimacy and national security and is designed to deter foreign intervention, especially from the US and South Korea. Diplomatically, Kim has leveraged nuclear capabilities to gain international attention, engaging in high-profile summits with leaders like Donald Trump, while never seriously compromising on disarmament.North Korea under Kim Jong-un also examines how, domestically, Kim maintains elite loyalty through a tightly controlled patronage system -- distributing privileges, purging potential rivals, and exerting strict control over the military and security services to ensure discipline and suppress dissent. It highlights that the Korean peninsula remains a potential source of major armed conflict in the region, with increasing risks, particularly as North Korea has resumed a historic alliance with the Russian Federation.