On 2 May 1944 a British staff officer doing the London Daily Telegraph crossword puzzle noticed 17 across: 'One of the U.S.' answer: Utah, the code name of one of the landing beaches. It was found that in previous months the words Juno, Gold and Sword (all code names for landing beaches) had appeared. On 22 May came the clue 'Red Indian on the Missouri': Omaha (landing beach). On 27 May the solution to ‘a Big-Wig' was Overlord. On 30 May the pattern continued with Mulberry (floating harbours used in the landings) and finally, on 1 June, the solution to 15 down was Neptune (code name for the naval assault phase).Text and image from Robs Webstek. Further details on this curious phenomenon from a 2004 story in The Telegraph:
An explanation of how the codewords came to appear in the paper emerged only in 1984. Following a re-telling of the "D-Day Crosswords" in the Telegraph, Ronald French, a property manager in Wolverhampton, came forward with further information. He said that, as a 14-year-old at the school in 1944, he inserted the names into the puzzles.
According to French, Dawe [the crossword compiler] occasionally invited pupils into his study, where, as a mental discipline, he would encourage them to help fill in the blank crossword patterns. Later, Dawe would create clues for their solution words...
French claimed that during the weeks before D-Day he had learned of the codewords from Canadian and American soldiers camped close by the school, awaiting the invasion.
"Everyone knew the outline invasion plan and they knew the various codewords. Omaha and Utah were the beaches they were going to. They knew the names but not the locations. We all knew the operation was called Overlord."
The soldiers talked freely in front of him "because I was obviously not a German spy. Hundreds of kids must have known what I knew."