It is the morning of 5 May 1945, on the wooded slopes of Gearhart Mountain in southern Oregon. The Reverend Archie Mitchell has driven his pregnant wife, Elsie, and five children from his Sunday school up for a picnic. As Archie parks the car, the others walk ahead toward Leonard Creek — and one of the children calls out that they have found something strange in the trees: a great, deflated balloon, tangled in the brush.

Archie shouts a warning. It comes too late. A powerful explosion tears through the little group, and in an instant Elsie Mitchell and all five children are dead.

They had been killed by a bomb launched from the other side of the Pacific Ocean, carried more than six thousand miles by the wind. They remain the only people killed by an enemy attack on the American mainland in the whole of the Second World War.

A weapon carried by the wind

Unable to reach the American mainland with bombers, Japan turned to something stranger: the newly understood jet stream, the river of fast-moving air high over the Pacific. Engineers built balloons roughly ten metres across out of layers of mulberry paper glued together by schoolgirls, filled them with hydrogen, and hung beneath each one a load of incendiaries and a high-explosive bomb.

An ingenious automatic system kept them aloft for the three-day crossing: as a balloon cooled and sank at night, it dropped sandbags of ballast to climb again. About nine thousand were released from the coast of Honshu between November 1944 and April 1945.

Hundreds of balloons, and a deliberate silence

Hundreds of the balloons completed the journey, drifting down across a vast area from Alaska and California to the Canadian prairies and as far inland as Michigan. They did remarkably little damage; the winter woods they fell into were too wet to burn. Crucially, American authorities imposed a near-total news blackout on the balloons. Hearing no reports of success, Japanese commanders concluded the weapon had failed and ended the programme in April 1945. The silence had quietly disarmed it.

The picnic at Gearhart Mountain

And then came Bly. The blackout that had blunted the campaign also meant that ordinary Americans had no idea these things existed — so when a group of children in the Oregon woods found one, they had no reason to fear it. The six who died that day were the campaign’s only casualties. Afterward, the authorities partly lifted the secrecy, warning the public to stay away from any strange balloon they might find. Today a stone memorial in what is now the Mitchell Recreation Area marks the place where they died.

It was a surreal weapon — paper and wind set against a continent — and it killed almost no one. But the six lives lost at a church picnic in the Oregon pines are a quiet reminder that even the war’s most distant front reached, just once, all the way home.

Sources: Smithsonian Magazine; HistoryLink.org; The Oregon Encyclopedia.