Did the Soviet Army have Segregation?

Edit: I see you beat me to it Comrade Gulper: actually there is some interesting info on the subject:

From an informative wiki article (original in Russian):

Quote:

National military units of the Red Army are military units of the Red Army formed during the Great Patriotic War on the basis of the nationality of their personnel. In addition to national units, members of all nationalities in the country also served in ordinary military units not formed on national or other grounds.

Since its inception, the Red Army included a tradition establishing military units on the basis of nationality (continuing the trend which existed prior to the revolution as well), however by the mid-1920s, their number was very small. On March 7, 1938, by special decree of the Central Committee of the Communist Party and the Council of People's Commissars 'On the national units and formations of the Red Army', a new nationwide regulation for military service was introduced for all the country's nationalities. [Ostensibly aimed at ending the existence of such formations ed. s78]

However, the difficult situation at the beginning of the war forced the government to step back from this principle. The formation of national units of the Red Army was re-started in August 1941, by the decision 383 of the State Defense Committee. The 201st Latvian Infantry division became the first such unit, and would consist 90% from inhabitants of the Latvian SSR, more than half of them being ethnic Latvians.

In the course of the war, national units were formed in 11 republics. In total, the Red Army saw the formation of 66 national military units - 26 infantry and mountain divisions, 22 cavalry divisions and 18 infantry brigades. Of the total, 37 of them participated in fighting on the front lines during the war.

In the course of their existence, many of these national units saw their numbers and their names changed, and in some cases saw the loss of their 'national' character. National units existed in the Soviet Army until the mid-1950s.

National composition of the Red Army

You can see the national breakdown of each of these units by translating the page using googletranslate.

In other words, national units did exist, but they were almost never purely one nationality or another, and in addition, members of a nationality could and did serve in general units of the Red Army, and in the agglomerations of armies, known as fronts (Comrade Gulper mentioned the 1st Ukrainian Front). The creation of national units was never an issue of segregation (which carries a negative connotation), but rather an organizational and logistical issue, based, for example, on national units' common language, or their geographic location (i.e. units stationed on the border with or in Iran would naturally be from neighboring Azerbaijan). Take note: there were no exclusively Russian national units formed, since it would have been both pointless and absurd (given the number of minorities inside the Russian republic of the USSR). For that matter, there were no exclusively Belorussian or Ukrainian units either.

You mentioned Poland, but take note: Poland was not a republic of the USSR; after 1917 they broke off and stayed broken off. During the Cold War, Poland, as an independent state, had its own national army, which participated in the defense of Eastern Europe along with the USSR as part of the Warsaw Pact.

As for the demographic breakdown in the link provided by Comrade Gulper: they include people from all across the USSR; for example, the Jews could have been from the Russian republic, or the Ukrainian one, or the Georgian one, or anywhere else. Naturally, it's most likely that minorities would be from their respective republic, autonomous republic or oblast - for example, the Chuvash would most likely be from the Chuvash autonomous oblast - a region inside the Russian republic; again, of course, they could theoretically have joined the army from anywhere within the USSR, if that's where they actually lived.