I believe that, for Mongolia, the major WW2 campaign was that of the Khalkh River (Khalkhin Gol) in May-August 1939 when a combined USSR-Mongolia force stopped the northern advance of the Japanese 6th Army. In addition to the initial Medal issued in 1940 (Battushig A39), the People's Khural (legislative body) authorized/issued commemorative medals (and ribbons) for the 30th Anniversary (Battushig A45), 40th Anniversary (Battushig A51), 50th Anniversary (Battushig A58; no ribbon), 70th Anniversary (2009, no ribbon) and 80th Anniversary (2019, no ribbon). There was no commemorative issued for the 60th (1999), perhaps due to political tensions and instability within the government/Khural at the time.
The Mongolian Ministry of Defense also issued (Army) Badges for Khalkhin Gol (Battushig C24), Victory of Khalkhin Gol (Battushig C25) and the 20th (Battushig A60), 40th (Battushig C26), 50th Anniversary (Battushig C23) and 65th (Battushig C27) anniversaries.
I am not familiar with any USSR medals issued for Khalkh River, but in 2019, Russia (a private mint, I believe) issued a commemorative medal for the campaign -- and (Russia) President Putin joined (Mongolia) President Battulga at a special ceremony on the battle site in Eastern Mongolia.
Interestingly, Japan (and Manchukuo) issued a "Border Incident" Medal as well -- for the decisive battle near Nomenhan village on the border between Mongolia and Manchuria (now China).
I apologize if this is "old" information, but I find it fascinating and have made a point of collecting them all, together with recipients' documentation.
