The American volunteer flyers who fought for China against the Japanese invasion were known as the 'Flying Tigers.' They saw their first combat on December 20th, 1941. They had originally thought this would be earlier, but various delays meant that it happened a few days after the US and Japan...
Both Germany and Japan came to use a similar solution for their nightfighters: obliquely mounted cannons.
As far as I'm able to find, both came roughly at the same time (1943, japanese slightly latter) but I do not come across any source that stated that there was any knowledge transfer between...