Nuclear powered submarines are often among the most complex and expensive systems ever fielded by any military. However, for decades, they (and less expensive conventionally powered designs) have been considered a cornerstone of naval power by many navies because of the unique capabilities they offer.With new anti-submarine threats emerging, from new sensors to unmanned systems, many nations are now preparing to design and produce a new generation of submarines to answer those threats, leverage new technologies, and keep up with international competitors. Today, we take a look at that emerging development and construction race.