The codes used by the president to launch a nuclear strike were mislaid for months during the Clinton administration, the former highest-ranking US officer has said. [...] Gen Shelton said the incident had taken place "around the year 2000". Under the procedures, an official was sent every month to check the codes, and that they were replaced every four months with new codes. According to Gen Shelton's book, Without Hesitation, an official had gone to check one month and been told by the aide that the codes were on the president's person but that he was in an important meeting...