Which of the following countries was most successful in its economic mobilization for WWII: Britain, the USA, Germany, USSR, or Japan?

This is a
very difficult question to answer
without detailed statistical analysis.  It depends to some
degree on what you
mean by "success."  If you are talking about sheer economic output,
then
surely the United States was most successful because it was able to produce such
huge
quantities of war materiel.  However, this seems like an inappropriate
measure because the US
was a much bigger country with much more economic
potential than any of the other
countries.

I would argue
that there is not much to distinguish between the

mobilization...