I had always thought that the Japanese didn't have a word for surrender before WWII. It seemed to be plausible given their culture. However, I can't seem to find any solid evidence of this. Is it just a myth?
降伏 （こうふく） is borrowed from Classical Chinese and probably has many centuries of history. After all, in the Sengoku period there were probably many, many surrenders of lords to other lords.
I think this question is relevant: What do you mean, "In Japanese there are no words for "I’m suffering""?
Also a little googling leads to a quote where this is clearly being used metaphorically by the speaker (presuming this is even an accurate quote/translation and not made up):
Captain Sasaki of the Yokahama Guards: "There is no such word as surrender in the Japanese vocabulary. Japan must fight! why should it surrender? There is still a huge Japanese army on the Chinese mainland, and Japan still holds 350,000 Allied prisoners of war."
This link talks about leaflets scattered during the second world war to encourage Japanese soldiers to surrender. Initial leaflets said "I surrender" but later ones said "I cease resistance", and were more successful. Whether or not this was really down to the implications of 降伏 versus more euphemistic terms is hard to say, but this is probably the original source of 'no word for surrender'.