Ditto that, and to add to it, more recently:
The Chinese "classics" that we now know from Chris Li and Stanley Pranin were being widely distributed thru Japan during the last century and the one before that.
Which gives the whole
Chen family lineage amongst a great many others
Boddhidarma when he visited China, so India
Pretty much the transmission of martial arts across all of Asia and other points
Its just who "didn't get" it and "who decided not teach it " or " who decided to leave it out or not teach it"
out their respective arts
Keep going back in time and you'll arrive at Alexander the Great invading India and teaching Pankration and πνεύμα theories to hindustanies. Maybe Arrichion, Polydamus, Dioxippus, et c. had Aiki. What about Achilles?