It consisted of separate revolutionary squads, mainly Bolshevik, Leftist and Anarchist, as well as small parts of the old Russian army, which had fought in World War I on the Romanian Front.
In the middle of February the Army was reinforced by 3,000 men of the Krasnogvardeysky detachment under command of Mikhail Muravjev, which arrived from Kiev.
The army repulsed attempts of the Romanians to get a bridgehead on the left bank of the Dniester River and on February 20 launched a counteroffensive.
On March 5–9, a joint protocol was signed on the cessation of the Soviet-Romanian armed conflict, under which Romania undertook to withdraw its troops from Bessarabia within two months and not to take any military or hostile action against the RSFSR.
Therefore, on March 9, Romania captured Akkerman, violating the reached agreement and completing the seizure of South Bessarabia.
Komdarm Mikhail Muravjev ordered the Special Odessa Army to stop the advance of the Austro-Hungarian troops along the south-western railroad.
Fighting broke out near the railway stations of Sloboda and Birzula on March 5–7, 1918 between Red troops and the 3rd infantry and 2nd Cavalry Divisions of the 12th Corps of the Austrian Army.
On March 12, the City Duma took over the power in Odessa and agreed with the Austrian command on the unimpeded evacuation of the Red Army.
It operated in the region of Perm, Yekaterinburg and Ishim against parts of the rebellious Czechoslovak Legion and White Guards units.
After restoring its fighting capabilities, the 3rd Army conquered a number of settlements in February 1919 and stopped the enemy's offensive on the Vyatka River.