The Battles of Khalkhin-Gol, the first installment in Days of Wonders second series of Memoir 44 Battle Maps, offers a campaign of six standard scenarios that can be enhanced with the two pre-printed Breakthrough battles provided in this expansion.

In more detail, The Battles of Khalkhin-Gol is a series of battles fought along the Halha River (Khalkhin-Gol) on the Soviet-Japanese border at the very beginning of World War II.
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 five 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 U.S. Marines and Japanese forces that took place years later; therefore, it is not part of the campaign.

This expansion also includes six Soviet BA-10 Armored Cars and six Japanese Type 97 Te-Ke tankettes that players will find useful for many of the scenarios included.

The Battles of Khalkhin-Gol is designed for 2 to 8 players. Each oversized map is ready-to-play with all terrain, obstacles, and unit positions pre-printed so players can simply add the figures and play. The various scenarios of the expansion require one copy of Memoir 44 (two for the Overlord scenarios), as well as the Terrain Pack, Eastern Front, and Pacific Theater expansions. The Equipment Pack and Winter Wars expansions are also recommended.