The U.S. National Security Agency (NSA) secretly spied on the leaders of European Allies, including German Chancellor Angela Merkel, using its partnership with Denmark's intelligence service, Reuters reported, citing Danish broadcasting. When the bombshell detonated, the whole world went into shock. How did this come to light? Let's start with the Prism scandal. In June 2013, Snowden leaked information about a massive secret US surveillance program code-named Prism. According to documents snowden provided to the Guardian, the agency monitored at least 200 phone numbers, including the calls of many world leaders.