The atrocious conduct of the Red Army following their conquest of Eastern Europe and East Germany was largely influenced by their blatant abuse of alcohol. In fact the NKVD allegedly reported back to Moscow complaining that 'mass poisoning from captured alcohol is taking place in occupied Germany' as it was seriously limiting their combat capabilities. Additionally, "It seems as if Soviet soldiers needed alcoholic courage to attack women". They were often so drunk they could not finish rapes, and in some cases used the bottle which caused devastating injuries (Antony Beevor, Berlin, 2007).

It should also be noted, compared to the other armies of World War Two, the Red Army's excessive drinking was linked to Russian culture:

[i]t was not the amount that Soviet soldiers drank that proved so disastrous for women - in comparion, for example to how much American soldiers drank - but rather the way they drank. As scholars of Russian drinking habits have repeatedly noted, Russians drink in binges, reaching a stage of intense intoxication over a period of several days, and they are quite sober before the next binge. The availability and high quality of alcohol available in Germany did not help the situation. One SDP informant recorded a hard and fast rule for dealing with Soviet troops: 'So long as he [the Russian soldier] is sober, one has almost nothing to fear Only under the influence of alcohol and also when several are drunk do the excesses begin' (Norman Naimark, The Russians in Germany: A History of the Soviet Zone of Occupation, 1945–1949, 1995).

Very major. Recently I was reading a book on the battle at Stalingrad and operation Uranus.

One of the sections mentioned that after German defenses were overrun in several cases, the Russians celebrated by drinking Vodka heavily. Later in the day Germans launched counterattacks and were met with no return fire. The Soviets were too drunk to react and the Germans re-took some of the positions.