Fire-balloon bombing campaign
In 1944 and into 1945, the Japanese launched an ambitious campaign of fire balloon bombs called "Fu-go" bombs with the intention of distracting Allied forces from the war effort. The scale of such a project was massive; over 9,000+ of these crude weapons were released from the Japanese mainland and drifted, through use of the jet stream, to the United States and Canada. The hope was to cause mass hysteria in cities and spawn forest fires in more remote places. Over 300 of these bombs were observed in the US and Canada, but the resulting hysteria failed to occur. This was partially due to a media blackout, requested by the government. It took about 3-to-4 days for the balloons to reach the American continent.
Silence was hard to maintain as more and more Americans grew curious about reports of sightings. Some were even found as far east as Nebraska and Michigan. Little damage resulted as a result of the campaign, but it was ultimately the death of 6 Americans in rural Oregon that forced the government to go public with the details surrounding the strange sightings.
The last balloon in their project was released in April 1945, as American forces began pushing to take Okinawa.