I wouldn't say martial arts were invented by the Japanese. They exist in almost all cultures, and not just Asian ones (savatte, fencing, krav manga, kung fu, boxing, the list goes on). The ones you mentioned are of course Japanese Maciamo, but strictly speaking one could even argue that Karate is not Japanese because it's roots are in Okinawa. The oldest Japanese 古武道 ie. old martial arts (meaning the traditional ones) are acknowledged to have come from China in any case. Japanese martial arts were originally battlefield techniques and ways of waging war so to say that the origin of 'martial arts' is in Japan is like saying war originates from Japan.