Beginning in May 1946, Scandinavian military authorities received an escalating series of reports from civilians and military personnel describing fast-moving, missile or rocket-shaped objects flying over Sweden, Finland, Norway, and Denmark. The objects were typically grey or metallic, cigar-shaped, and sometimes with a tail of fire or vapor. By summer 1946, the Swedish Defence Staff had formally designated these 'ghost rockets' and deployed specialized radar units and camera stations. Between July and August 1946 alone, 997 reports were logged. The Swedish Air Force Chief of Staff briefed the government. Sweden formally requested intelligence sharing from the United States, the United Kingdom, and the Soviet Union. The British Air Ministry sent an observer team; US Army Air Forces intelligence personnel were also consulted. Some objects appeared to crash into Swedish lakes, and Swedish military divers conducted searches. Fragments were recovered from Lake Kölmjärv in August 1946; Swedish engineers analyzed them but the composition was not publicly disclosed. By December 1946, the Swedish Defence Staff issued a final assessment: the objects were real, physical, and not weather phenomena, balloons, or astronomical events. Crucially, the assessment also concluded the objects were not Soviet V-2 derivative rockets — the flight profiles, speeds, and lack of impact craters at supposed crash sites did not match. The full Swedish investigation files were partially declassified in the 1980s and are held in the Swedish National Archives (Riksarkivet).