By Richard H. Hall
Source: National UFO Reporting Center, Davenport, Washington
Quote from the article:
“A particularly interesting series of UFO reports came from the vicinity of the ‘Operation Mainbrace’ NATO maneuvers held in September 1952. The maneuvers commenced September 13th and lasted twelve days. According to the U. S. Navy, ‘units of eight NATO governments and New Zealand participated, including 80,000 men, 1,000 planes, and 200 ships . . . in the vicinity of Denmark and Norway . . . .’ Directed by British Admiral Sir Patrick Brind, ‘it was the largest NATO maneuver held up until that time.’
September 13–The Danish destroyer Willemoes, participating in the maneuvers, was north of Bornholm Island. During the night, Lieutenant Commander Schmidt Jensen and several members of the crew saw an unidentified object, triangular in shape, which moved at high speed toward the southeast. The object emitted a bluish glow. Commander Jensen estimated the speed at over 900 mph.
Within the next week, there were four important sightings by well-qualified observers. (Various sources differ by a day or two on the exact dates, but agree on details. There is no question about the authenticity of the sightings; the British cases were officially reported by the Air Ministry, the others are confirmed by reliable witnesses. All occurred on or about September 20).”
20 September 1952 Operation Mainbrace UFO photo (nicap.org)