To derail the thread temporarily - it's amazingly difficult to determine with any accuracy just what proportion of "budget" went to the military at any time during the existence of the USSR. My background is in economic history and I find the ins and outs of the arguments about the details of Soviet military spending a fascinating subject.
US intelligence assessments of military spending in the USSR during the mid 1980s ranged from low end figures in the range of 12-15% of GDP, mid range estimates of 17-24% and upper range estimates in the 30-38% range. In 1985, spending in then current US dollars was estimated at anywhere as low as $175 billion all the way up to about $330 billion.
From the mid 1970s and into the tail end of the 1980s, the CIA and DIA were basically at loggerheads with academics and economists about how to properly estimate the size of the Soviet economy and what the actual level of spending was that they were lavishing on the military. The intelligence agencies generally gave quite low GNP estimates but figured that military spending was 50% of the state budget, or a little more. The academics were a bit more varied, their GNP estimates had a much greater range (as little as 1/2 of that of the intelligent agencies to 3x as much) and their estimates of military spending were generally much more conservative. However, there was also some very outspoken academics who thought the CIA/DIA methodoligies were underestimating Soviet GNP and military spending.
If anyone feels like chasing some odd rabbits down weird holes:
EDIT: For anyone that reads Russian (or has a good machine translator they like), here's some Russian estimates about defense spending:
