Of course there was Great War for them but only since 1941 . They dont remember that in fact WWII begun in 1939 - when they were also one of the agressors and occupants. 1.09. 1939 Germans invided one part Poland , then 17.09.1939 Soviets invided the second one (according to Ribentrop-Molotov pact).
http://en.wikipedia.org/wiki/Treaty_...e_Soviet_Union

30.11.1939 Soviets try to invided Finland.
http://en.wikipedia.org/wiki/Winter_War

Since 1922 (Rapallo) till 1941 Germans and Soviets was constantly cooperating very close. So their "divorce" begun only in 1941.
http://en.wikipedia.org/wiki/Treaty_of_Rapallo_(1922)

As its seen on attached photo, many of them still using red flag (with hammer and sickle) - symbol of comunistic totalitarism on the official celebrations. The symbols of the second - nazi (nazi=national sozialismus) - totalitarism in Germany are forbiden.