The Tunguska event in 1908 hit St. Petersburg instead of the wilderness, killing the entire Russian royal family. Russia collapsed into anarchy, and Germany sent in peacekeepers and humanitarian workers. This is how German scientists in St. Petersburg discovered 'astronium' and 'petrinium', mysterious new elementselements brought with the meteorite. These elements allow scientists to make powerful bombs, create free energy, and even build torch-ships that allow space travel, especially after these elements were found in other meteor craters around the world.
It is now 1938. WWI never happened, and the new space industry shortcut the Great Depression. The US, Germany, Britain, and Japan have permanent space stations; Britain has colonised Mars, France is busy exploring the oceans of Venus, and the Italians are mining Mercury. All major powers have bases on the moon with mass drivers pointed at each other's capitals, thus preventing war from breaking out.