Generally, I know that the interests of Germany and Japan first came together to stop the spread of communism, but what were some of the other reasons and interests of the parties that led to the ensuing negotiations.
The main reason was to keep the USA from directly joining the war on Britain's behalf. The idea being the US would be less likely to declare war on Germany if they knew it would also mean having to fight a simultaneous war with Japan on the other side of the world.