Top-secret documents expose the controversial role of a massive NSA surveillance base in England's countryside. For years, journalists and researchers have speculated about what really goes on inside Menwith Hill, while human rights groups and some politicians have campaigned for more transparency about its activities. Now, however, top-secret documents obtained by The Intercept offer an unprecedented glimpse behind Menwith Hill’s razor wire fence. The files reveal for the first time how the NSA has used the British base to aid “a significant number of capture-kill operations” across the Middle East and North Africa, fueled by powerful eavesdropping technology that can harvest data from more than 300 million emails and phone calls a day.