The physical Soviet presence, and corresponding western impotence, and unscrupulous Soviet disregard of the Yalta and later agreements, led to the consolidation of the "Soviet sphere of influence" in Eastern Europe. The process had begun when the Red Army overran Poland (part of which was seized by the USSR under the 1939 Nazi-Soviet Pact) in the summer of 1944. Its culmination, following Soviet rejection of the Marshall Plan in 1947, was the communist coup d'etat in Czechoslovakia in February 1948. It is noteworthy that just as no act at Yalta underwrote a Soviet sphere of interest in Europe, so none had assigned Czechoslovakia to such a sphere. The West's conclusion of the Brussels Treaty in March 1948, with firm US and Canadian support; the creation of a West German state; and the establishment of NATO in April 1949, were the perhaps inevitable Western responses and a further manifestation of the division of the continent .