What did the United States Army use during Operation Peppermint to prevent the Germans from  disrupting the 1944 Normandy Landings?
Operation Peppermint Operation Peppermint was the codename given during World War II to preparations by the Manhattan Project and the European Theater of Operations United States Army (ETOUSA) to counter the danger that the Germans might disrupt the June 1944 Normandy landings with radioactive poisons.
Operation Bolero Operation Bolero was the commonly used reference for the code name of the United States military troop buildup in the United Kingdom during World War II in preparation for the initial cross-channel invasion plan known as Operation Roundup, to be implemented in mid-1943, or for its lesser contingency alternative, Operation Sledgehammer, to be executed in the fall of 1942 in the event of German setbacks or to ease Axis pressure on the Eastern Front. ("Bolero" was the code name used in official communications to stand in for "United Kingdom" when describing the theater or movements.) What later became the Bolero plan – the buildup of a strategic air force in Great Britain in preparation for Roundup – was first submitted by Commanding General of the U.S. Army Air Forces, Henry H. Arnold, to General George Marshall, the U.S. Army Chief of Staff, on April 12, 1942, and set in motion a huge movement of men and material that laid the groundwork for Operation Overlord.