Dear Reader, Our Munich Security Report, which we first published in 2015, is our conversation starter for the Munich Security Conference and aims to serve as a useful compilation for decision makers, security professionals, and the public. In anticipation of the Munich Security Conference 2018, we are pleased to present the report's fourth edition. In the last year, the world has gotten closer-much too close!-to the brink of a significant conflict. Tensions between North Korea and the United States have greatly increased and rhetoric on both sides has escalated. The relationship between Saudi Arabia and Iran is showing a similar dynamic, manifesting itself in further regional instability. In Europe, tensions between NATO and Russia remain high, and the war in and over Ukraine continues unabated. Moreover, landmark arms control treaties, such as the Intermediate-Range Nuclear Forces Treaty, are at risk of unraveling, while efforts to limit arms races in new fields, such as cyber, are stalling. This is all taking place against the global backdrop of rising nationalism and illiberalism, weakening some of the core principles of the international order. So far, most of today's contentious relationships and disputed issues have not come to a head. 2018 promises to be a year where some of these crises might either move towards resolution or escalation-with potentially catastrophic consequences. We must do whatever we can to move away from the brink. This report aims to make sense of today's security environment by presenting condensed information on some of these crises and, more generally, on some of the most important actors, regions, and issues on the international security agenda. As in previous editions, the list of topics is neither comprehensive nor exhaustive. This report would not have been possible without the generous support of the numerous renowned institutions, friends, and partners who made their research and data available to the Munich Security Conference. I would like to thank them all-and wish you an interesting and thought-provoking read! Sincerely yours,