Shamefully, there was no public Western pressure put on Stalin to open any sort of Second Front on Japan from the North, during the desperate days of mid 1942 or ever after.
Ever after, as in : no major postwar historical school has ever focused on this baneful fact.
Instead Japan and Germany successfully held back, retreating very slowly, while being attacked on only two major fronts at a time.
(They themselves succeeded best when they only attacked on one major front at a time.)
Yet Germany and Japan rapidly fell apart when they were under attack on three major fronts all at once.
In 1944, Germany fell apart the moment it had to supply artillery shells to three major battle zones : in the East, in the West after D-Day in France and in the South as the twenty nation Allied army continued its push into Vienna and Munich via Italy.
In August 1945, Japan also suddenly fell apart when it was under attack on three fronts : in the Pacific from the USA, in the East by the Chinese and British Burmese Army, and now in the North from the USSR.
The Russians only fought Germans and were so carefully neutral towards Japan they won't allow US flights over Soviet airspace en route to Japan ---- even the Swedes and Swiss were far far less neutral than that, to the German war machine.
The British basically only fought Germany and Italy, on land.
The USA fought Japan, Germany and Italy full out, on land, from the Fall of 1942 --- but not decisively, until late 1944, because they lacked support from their other major allies and faced a divided American military brass and public.
Churchill (Italy) and MacArthur (Philippines) share the blame with Stalin
Both Germany and Japan needed to face three major land battles at a time to lose, though one major battle front and two minor battle fronts all at the same time might also have spelt a faster doom.
Interesting to imagine the combined effect of a major American landing in the South of France at the same time as a minor British Commonwealth landing in Sicily and a huge Russian offensive against Germany, if tied simultaneously to a major Burmese Army/Chinese offensive and a small Russian advance into Manchuria via Mongolia, coupled with an American bomber campaign from the Aleutians and a land attack on an Japanese island very near to the Japanese main islands.......