Pavlov was Commander of the Western Front when the Germans invaded Russia. A tank expert who had served in Spain and in Finland on the Mannerheim Line, he believed that tanks had a merely subsidiary role as infantry support. In 1940 Pavlov was appointed Commander of the Western Military District (renamed the Western Front on 23 June 1941) which covered Northeastern Poland, and the Bialystok and Brest-Litovsk regions. In June 1941 Pavlov faced GUDERIAN’s 2nd and 3rd Armored Groups with equal infantry strength but low numbers of tanks, one half of which he lost in the first day’s encounter. By 28 June his defenses had collapsed and he was replaced by YEREMENKO. Pavlov, his Chief of Staff, and his Fourth Army Commander, Korobkov, were all shot for incompetence.