This book states that burden-sharing is one of the most persisting sources for tension and disagreement within NATO (North Atlantic Treaty Organisation). It also belongs to one of the most studied issues within NATO with distinguishable traditions and schools of thought. However, this pertinent question has been rarely discussed extensively by academics. The key idea of the book is to make burden-sharing more understandable as a historical, contemporary and future phenomenon. The authors take a comprehensive look at what is actually meant with burden-sharing and how it has evolved as a concept and a real-life phenomenon through the 70 years of NATO’s existence.