The Kwantung army was responsible for all of China, including Manchuria. I far as I can tell, their AO was from the Kuriles and Sakhalin in the east all the way past the Mongolian borders to the west, to central China in the south. The Russians attacked as a front with three major axes of attack, each of which was astoundingly successful. As there were only two sides fighting, it was definitely the Kwantung Army, a unit of the Imperial Japanese Army, which did all the surrendering. This mass surrender would have been received by the Russians, or if none were available, by local chinese civil authorities. (I would imagine).
There is a very interesting theory as to why this campaign has received so little publicity. Many of the admittedly few sources that I have read have stated that this was, in fact, the greatest campaign ever mounted in terms of the amounts of men and equipment fielded in a single attack. At the time, the Russians were also seen in the west as the emerging red menace, so few, if any researchers were ready to baldly state that the Red Commie Russkies had mounted a campaign that the mighty US military could not even imagine doing. So, it was simply ignored here in the west, and the accomplishment was seen as a communist land grab against a poor helpless Japanese army that was simply unable to resist - given that the war was, for all intents and purposes, over. Of course, this view really is nothing but bovine fecal matter, but it was the prevailing view until after the fall of the iron curtain. (Believe it or not, this is how I read it as an adolescent!)
Most of the sources that I have seen do not seem to be 'tainted' by the PRC at all. The PRC did not exist at the time, it was merely a rebellion, and the Nationalists were not very active in the border regions.
A decent but rather short source of information can be found at
http://www.globalsecurity.org/military/library/report/1995/HAL.htm
Bulldogg, I hope that you publish the stuff that you got from those interviews. Those people have been completely ignored by history, as all of the informations seems to have come from headquarters level and higher. Interesting, but very one sided. You have the makings of a very interesting book that I would buy.
Dean.