It spent the bulk of World War II guarding the border in that area, sending formations to the Eastern Front while undergoing several reorganizations.

The army, redesignated as the 2nd Independent Red Banner Army (2nd OKA), still under Konev's command, was headquartered at Khabarovsk and controlled troops in the oblasts of the Lower Amur, Khabarovsk, Primorsky, Sakhalin, and Kamchatka, the Jewish Autonomous Oblast, and the okrugs of Koryak and Chukotka.

It was directly subordinate to the People's Commissariat of Defense and operationally controlled the Amur Red Banner Flotilla.

[4] The 2nd OKA included the 3rd, 12th, 34th, 35th, 69th, and 78th Rifle Divisions during its existence,[5] as well as the fortified regions of De-Kastri, Lower Amur, Ust-Sungari and Blagoveshchensk.

[6] Elements of the army fought in the Battles of Khalkhin Gol, a series of border clashes between the Soviet Union and Japan, in mid-1939 under the control of other formations.

[11] During World War II, the army covered the border around Blagoveshchensk and sent reinforcements to the active forces fighting on the Eastern Front.

[9][7] On 28 June the 31st SmAD departed for the Eastern Front, and remaining units, including the 3rd Fighter Aviation Regiment, were made directly subordinate to the Air Force (VVS) of the 2nd KA.

When the main Soviet attacks achieved success,[35] the army was to launch an assault crossing of the Amur River, reduce or isolate the Japanese Sakhalian, Aihun, and Holomoching fortified regions and defenses around Sunwu, and advance south through the Lesser Khingan Mountains to Qiqihar and Harbin.

[13] An operational group consisting of the 3rd and 12th Rifle Divisions, and the 73rd and 74th Tank Brigades, was positioned in the army's center and on its left flank.

The army's 101st Fortified Area, with artillery and machine gun battalions, was positioned on the Amur between the two groups to conduct supporting attacks.

The main bodies of the operational groups were placed in concentration areas, located 12–17 miles (19–27 km) in the army's rear.

Due to the rapid advance of the other Soviet forces, Purkayev ordered the army late on 10 August to begin its attack early on the following morning.

[37] The attack began early in the morning under the cover of an artillery bombardment, as reconnaissance and assault detachments from the first echelons of the operational groups crossed the Amur, capturing bridgeheads near Sakhalian, Aihun, and Holomoching, coming into contact with Japanese outposts and covering forces.

Forward units continued to engage Japanese advanced positions south of Holomoching and north of Aihun on 12 August, as reinforcements landed.

Meanwhile, the 74th Tank Brigade, reinforced by a rifle company, artillery battalion, and an antitank regiment, moved south and bypassed Sunwu, advancing to cut the Sunwu–Peian road.

Taking advantage of the tank attack, the 396th Division and 368th Regiment advanced on Sunwu from the north, surrounding most of the 135th Brigade in the Aihun Fortified Region.

After further heavy artillery and bombing from the Soviet 18th Mixed Aviation Corps of the 10th Air Army, Japanese resistance slackened on 17 and 18 August, and many defenders surrendered or were destroyed.

[39] The Japanese around the fortified regions were the most formidable faced by Soviet troops in the campaign, according to renowned historian David Glantz .