As I understand it, no occupation or war was necessary for the Japanese to learn to make bread from the Portuguese in the 16th century, and they still call it pan [citation needed] today. And tempura also developed from Portuguese ingredients around the same time, the name included.
Japan has not only imported all sorts of Chinese foodstuff and coocking techniques, but curry from India as well, though they make it mild.
The only thing Japan seems to ignore are cooked tomatoes, though they use the cherry variety in salads and bento boxes, it seems, as I was told in this thread.
ETA: Oh, yes! And German beer, they adopted that one too. And still brew an acceptable concoction to this day. No occupation involved in that one either.