One of the great debates among sake fans with too much time on their hands is whether sake that has alcohol added to it is real sake. It is interesting to look at the history, technical facets and economics of this issue.
First, a history lesson. Until World War II, all sake was made from rice alone. When rice became scarce, the government forced brewers to cut their product with lots of alcohol, thus allowing them to manufacture sake using much less rice. This enabled the industry to survive (just barely), while not squandering Japan's much needed staple food.
After the war ended and rice stocks returned to normal levels, the requirement was lifted. But by this time, brewers had discovered a much more profitable way to make sake, and so the practice of increasing yields in this way was never discontinued. In fact, it wasn't until 1964 that anyone began brewing rice-only sake again.