Is this a multiple choice question? If so what are the options?
If it isn't, then you might say the fact that most of Eastern Europe is flat has historically caused the Russians to seek dominance over their neighbors, in order to put as much distance between their enemies and their 'motherland,' because there are no natural obstacles (like mountains) to slow the advance of their enemies in the event of war. You can see this in both the Russian Empire, which colonized much of Eastern Europe, including Poland, Ukraine, Belarus, etc, as well as the Soviet Union, which turned many neighboring states into satellite states after World War II.
Hope this was helpful.