Khalkh is the largest river in Dornod area. The west bank of the river is taller than the east bank. If you see from the east bank, it looks like wall that covers over, so that it is called as “Khalkh” river which means “shield” in Mongolian. The Khailaast River flows into the Khalkh River. In 1939 an undeclared war was held between Japan - Manchu and The Soviet Union – Mongolia near the Khalkh River. The Soviet Union-Mongolians ended up winning the battle.