By this time, Los Alamos had begun developing nuclear anti-missile weapons of its own, updated versions of the 1960s Casaba/Howitzer concepts. Given the constant stream of news about Excalibur, they added a laser to one of their own underground tests, shot "Correo", also part of the Fusileer series. The 2August 1984 test used different methods to measure the laser output, and these suggested that little or no lasing was taking place. George Miller received a "caustic" letter from Paul Robinson of Los Alamos, which stated they "doubted the existence of the X-ray laser had been demonstrated and that Livermore managers were losing their credibility because of their failure to stand up to Teller and Wood."