This Chapter introduces the focus of the work. It explains that international adjudication has come under increasing criticism and backlash in recent years, and links this to long-lasting debates about the proper reach of international law and adjudication. The Chapter explains that adjudicative deference to States has been frequently identified as a possible option to respond to these concerns. The Chapter thereafter connects deference to debates about State sovereignty and autonomous decision-making authority. It introduces the structure of the book and identifies the key audiences and benefits to which it is directed, as well as how it differs from existing scholarship on deference in international adjudication.