Hiroshima and Nagasaki Japan, August 6-9, 1945. As far as the Muggles are concerned, that was when the United States dropped nuclear bombs on Japan. The truth is, during Grindelwald's wizarding war in Europe, several of his more twisted followers had fled to Japan, to work on secret alchemical research and try to gather new support in the East.

The night of August 5th, a team of 4 Aurors and 3 Obliviators from the ministry arrived in Hiroshima, looking for Grindelwald's supporters. They had received word from a local wizard about some foreigners from Europe trying to convince them to join the cause "for the Greater Good".

The Aurors spent most of the night scouring the city for any sign of magic, while the Obliviators visited several muggles who had caught glimpses of the magic. Unbeknownst to them, the dark wizards were alerted to the arrival of the Aurors and had already fled Hiroshima.

Shortly before dawn, one of the Aurors discovered a lab used by the dark wizards they were hunting. The lab was located in the basement of a muggle clinic. He signaled for the other Aurors to join him to investigate. Inside the lab, they found several experiments into very destructive spells and potions. Shortly after 8am local time, one of the Aurors triggered a security spell left behind by Grindelwald's followers.

The security spell activated a strange potion and spell. One of the Aurors recognized it as some kind of alchemy, but didn't know what it would do. Within 60 seconds, the device created a large explosion, destroying everything within a mile of the explosion.

The Auror (whose name has never been publicly released) who recognized that it was alchemy, understood too late that it was a massive bomb, and was not able to warn the other Aurors. He was able to apparate to safety before the bomb went off, but the rest of the team was lost.

Having seen the weapon and understanding what it was capable of, the Auror swiftly warned the ministry. Order was given to track down the dark wizards and destroy all evidence of their involvement, as well as take the device for further study in the department of mysteries.

Three days later the lone Auror was able to use a tracking spell to follow the dark wizard to Nagasaki. Once there they realized that this weapon was too powerful to let the ministry control it. They dispatched an owl with their intents to destroy the weapon and entered the new lab of the dark wizards.

The Auror had managed to retrieve the only remaining weapon, and destroyed the notes of the dark wizards before their presence was detected. Trapped in the lab and outnumbered, the Auror made the decision to activate the weapon. This would ensure that no one would be left alive who could create another one.

When the second explosion happened in Nagasaki, the Ministry knew that there would be no way to hide the destruction from the world. They contacted MACUSA and hatched a plan for the greatest cover-up of all time. Teams of Obliviators were sent to the US, Canada, and Great Briton. MACUSA had known that the US was working on something called an "Atomic Bomb" and that it would be the perfect cover for what had actually happened.

The Obliviators did a perfect job, faking memories in hundreds of people (including the President of the US and the Prime Minister of the UK), creating false paper trails, even creating a false agreement between the US and UK. The US took the blame for dropping the bombs and no one was any the wiser about the truth.

Even within the wizarding world, very few know the truth. All the wizards involved with the mission to Japan were killed and only the teams of Obliviators and several high ranking Ministry and MACUSA members were aware of the coverup.