The North Atlantic Treaty Organization (NATO) has a renewed focus on defense and deterrence in Europe. In the past, NATO relied at least in part on its military technological superiority over potential adversaries for defense and deterrence in Europe, but some policymakers are increasingly concerned that NATO's technological superiority is eroding. Russia, China, and others are modernizing their militaries, investing in new and emerging technologies, and exploring their applications for defense. In addition, NATO faces rising operating costs, and both conventional and hybrid challenges in operating domains that have expanded to include cyberspace as well as land, sea, and air. NATO must also contend with a growing group of nonstate challengers empowered by the pace of technological change and the global diffusion of technology. Increasingly dependent on ubiquitous technology, NATO is adapting to a world in which commercial investments in research and development (R&D) outpace those of governments, innovation cycles are shortening, and there is more international competition for technology and innovation. Since 2014, the United States has promoted defense innovation as a strategy to integrate new technologies into military capabilities and strengthen U.S. technological superiority over its potential adversaries. Today, many European allies acknowledge the importance of technology and innovation in defense, and they are beginning to respond to the changing environment by committing more resources to defense, and a few have national defense innovation strategies of their own. The United Kingdom, France, and Germany-NATO's largest European defense spenders-are investing more in R&D and reforming their defense ministries to take more risk, procure technology faster, develop innovative concepts, and strengthen their links with commercial industry. Generally speaking, however, European governments are still in the early stages of developing what are predominantly national strategies. NATO seeks to harmonize the allies' national strategies and defense investments, promote collaboration, and build a shared vision for the future. Its member states have sophisticated militaries, institutional frameworks for collaboration, and dynamic economies that attract talent, and support innovation. Innovation challenges persist, however, such as those related to NATO's limited budgets and its bureaucratic processes, which make it difficult for NATO to attract the attention of commercial industry and global technology companies. NATO is also working to balance its member states' concerns over national sovereignty with the need for more multinational cooperation, both from a cost and from an interoperability point of view. NATO also seeks to enhance interoperability among allied militaries and balance short-term priorities with preparations for future warfare. In the future, NATO might have to rely as much on its agility and on its capacity for innovation as it has relied on its military technological advantage in the past. Congress may consider what role the United States can play to support NATO's adaptation, and what channels Congress could pursue to exert influence over NATO's direction. There are both risks and opportunities associated with sharing technology or developing it jointly with NATO allies, and there are questions about what the United States and its allies expect from one another in terms of technology and innovation. Technology has the potential to enhance NATO's effectiveness, but it also has the potential to undermine interoperability or political cohesion if the United States develops a technology-driven strategy and its NATO allies either do not keep pace, or do not adapt to strategic, political, and technological change.