Poland has very few Russians.
Russian minority in Poland consists of 13,000 people (according to the Polish census of 2011)
In the past - the times of the Second Polish Republic, partitions of Poland and the Polish-Lithuanian Commonwealth - the number of Russians within Polish borders was much higher, over 100,000.
But the current number is enough for Putin to send in troops under the guise of protection.
Poland was a part of the Russian Empire, and that’s Putins goal, to reestablish Czarist Russian Empire.