The article analyzes the specifics of the establishment and functioning of the southeastern Soviet republics in the territory of Ukraine (Donetsk-Kryvyi Rih Soviet Republic, Odesa Soviet Republic, and Soviet Socialist Republic of Taurida) in 1918, as well as “LPR” and “DPR” in 2014; shows their specific participation in Russia’s hybrid warfare against Ukraine in a symmetrical comparison. The author emphasizes that the formation of these republics was a means of Bolshevist aggression in the early 20th century. Historical parallels and consequences are drawn between the Russian-Ukrainian wars of 1917–1921 and the most recent war (since 2014), their prerequisites, common features and war-waging experience. It is alleged that the activities of Soviet quasi-states had a common feature: they were created by analogy with the RSFSR, thus violating an important condition that required coordinating such actions with the expressed will of the entire population of the territory. The pseudorepublics even did not consider themselves formally Ukrainian, although the majority of their population was Ukrainian. This fact, as well as the thoughtless social and economic policy, confiscation of private property in the public interest, sending echelons with bread to the north, public fundraising (indemnity), abolition of commodity-money relations, and the introduction of labor control disorganized all spheres of life. Today it is evident that the Russian leadership is trying to destroy Ukrainian independence and revive the great imperial state. The present-day hybrid Russian-Ukrainian warfare is not, to a large extent, a new type of aggression. Putin’s policy is very similar to the Bolsheviks’ actions 100 years ago: we see the same creation of parallel puppet “authorities”, their subsequent provision with military assistance, and thus formation of the external aggression as “internal civil war”, or “brotherly assistance”, etc.