Norway is on the verge of buying new submarines. This study is an unclassified strategy analysis of why submarines should be part of the Norwegian Navy in the future. Due to shifting strategic circumstances, long-term defence planning is demanding. Preparing for a large-scale, high-intensity conflict is very different from handling a terrorism threat or low-intensity conflict, and it is difficult to foresee which capabilities will be most needed. Instead of looking at potential threat scenarios or technological options, this study takes as its departure point the protection of permanent Norwegian interests, such as security, economy and energy. This analysis is therefore aimed at identifying the submarines’ ability to secure such interests in war, crises and peace respectively. Key findings suggest that conventional submarines play an important role in providing Norway with a credible deterrent. With their ability to remain undetected for a long time whilst at the same time carrying highly effective weapons, the submarines enable even a small country as Norway to set a defence threshold against a powerful counterpart. Securing Norway’s vast coastline, modern submarines represent a capacity no nation can oversee or easily defeat, thus contributing to stability and peace. It is likely that a new class of submarines will play a pivotal role in protecting Norwegian interests.