 Complete the following phrase:  During the joint GermanSoviet invasion of Poland, which started World War II, in September 1939, Opatów was invaded and afterwards occupied by Germany. In 1939, the Germans ordered the demolition of the Ludwik Zwierzdowski monument, so the local mayor buried it to preserve it, thanks to which it was restored after the war. In 1940 the Germans carried out mass arrests of Poles as part of the 