The Japanese Sixth Army was facing the Soviet 57th Special Corps, including Mongolian cavalry. At first, the battles were only short skirmishes, but it soon escalated into open war. The whole campaign lasted 5 months and ended with a Soviet victory.
The six standard scenarios of this expansion can be played separately or as a campaign, with each scenario outcome impacting the following one. The pre-printed Breakthrough scenarios, Bain Tsagan Heights and Tightening the Noose, can be played in the campaign as well as one of the two Overlord scenarios, Encirclement at Khalkhin-Gol.
The second Overlord scenario, Cape Torokina Landings, highlights the fierce battle for Cape Torokina between US Marines and Japanese forces that took place years later - therefore it is not part of the campaign.