Chapter 7 explores how the proliferation of intelligence agencies during the Cold War brought into prominence the practice of international espionage, surveillance and covert intervention. As the 1960 U-2 incident exemplifies such practices were often the subject of significant contestation as to their legality in time of peace. Whilst the practice of surveillance was encouraged by an expanded concept of ‘national security’ it was often accompanied by a paradoxical commitment to secrecy. As secrecy intensified, public awareness of covert activities grew, and alongside it, accompanying practices of plausible deniability and ideological disavowal that undermined trust not just in public knowledge but in the possibility of legal judgment. We recount how contestation over the legality of espionage led, not only to a blurring of the categories of peace and war, but to the formation of a new legal framework for outer space that provided legal cover for ongoing surveillance to be undertaken by the rival Cold War powers. These developments profoundly impacted international law, sovereignty concepts, and global surveillance practices, shaping modern notions of global policing through surveillance and leaving a complex legacy in international relations.