When I played the Battle Zone II video game in the late 1990s, which was plotted around a war between a New Soviet Union and a future analog of the USA, I noticed that Russian tanks and pilots frequently exclaimed "For Mother Russia!".
This made me quite curious because not only the expression does not exist in Russian, but also would sound awkward.
Under the USSR it was very uncommon to call the USSR "Russia" especially by loyal citizens, those who were outside of the emigrant and dissident circles. Thus a common expression would be "For the Motherland!"("За Родину!") or (in more official style) "For our Soviet Motherland!"(За нашу советскую Родину!).
But the case is that the expression would sound awkward not only in the USSR, but in modern Russia as well (one can say "For Russia!", although this is uncommon, but "For mother Russia" sounds very much strange).
The expression also could not have come from Czarist Russia as well, it was common to call "За Отечество!" (can be translated "For the Fatherland!") those times.
I have seen the expression "For Mother Russia!" many times since then, but always only in English.
So my question is where did this expression came from and why it is so widespread in English?