This is about the event. For the monster, click here.
The Robo-Dactyl-Zilla attack was what caused the Japanese island Osalamisempei to sink in 1923.
On September 12th, 1923, a Japanese mad scientist on the lowermost region of Australia, Arizona created and released his most evil invention; the Robo-Dactyl-Zilla. This was a crossbreed of an android pterodactyl and Godzilla. It attacked the city-island of Osalamisempei, Japan, which no longer exists due to this attack. There were no survivors, so there is only a theory of what occurred on this dreadful day.
The Theory Edit
The most widely-accepted theory of this attack is as follows;
Robo-Dactyl-Zilla was released early in the morning and was programmed with one mission: destroy Japan. It flew to Japan's southern most island-city, Osalamisempei in three-and-a-half hours max. It started its attack by blasting the city, killing half of its population, resulting in what would become Japan's population problem today through a butterfly affect. The half of the island it didn't blast were eaten in a short amount of time. Robo-Dactyl-Zilla's devouring was its downfall, as the Japanese government quickly found out about the attack and sent their experimental Supreme Nova Atomic Wide-Range Bomb (or SNAWRB) to the island, both fatally wounding Robo-Dactyl-Zilla and sinking the island due to the bomb's tremendous power. Robo-Dactyl-Zilla had just enough energy to fly home, where it was killed by the U.S. government who had recently captured the mad scientist. However, they then started a program after this creature in an effort to create the ultimate war machine, along with their sister program, the Titan Program, which created Titans based on the manga and anime, Attack on Titan. The government sent its egg cells to the Titan program, where they were used to create Robo-Dactyl-Zilla Titan.