Another respectable source, Polish online encyclopedia http://encyklopedia.pwn.pl/16444_1.html says 300 thousand. But it's not clear whether they are only ethnic Poles or all polish citizens. Anyway, much less than 2mln (but not little too). I wouldn't say that Polish government in London gave those exaggerated figures on purpose. After katyn and after Soviets stopped recognizing legal polish authorities they had good reason to expect everything from the russians.
Another respectable source, Polish online encyclopedia http://encyklopedia.pwn.pl/16444_1.html says 300 thousand. But it's not clear whether they are only ethnic Poles or all polish citizens. ==
Think they say about only poles. All numbers of resressed on western Ukraine and Bellorussia probably is as MEMORIAL tells about 700 thousands. But those people wasn't killed. Probably part of them was executed by NKWD, it is unfortunately true:(. Most was just resettled as many small ethnicities from Caucausus and later during time of Kruschev returned back.
It is guilt of Stalin's repressions. As I many time said it was guilt of all soviets not only russians.
Accually the first russian in charge of USSR was Michael Gorbachev whose policy fred Poland and disbanded USSR. It was legal decision of Russian Federation which really disbanded USSR. SO russians destroyed USSR.
Before Gorbachev it was ukranians mostly beginning from Khruschev. Before them it was Stalin the georgian.