 Complete the following phrase:  Following the Axis invasion of Yugoslavia in April 1941, Germany placed Serbia proper under the authority of a military government to maintain control over important resources. Those included two major transportation routes, the Danube River waterway and the railroad line connecting Europe with Bulgaria and Greece, along with nonferrous metals that Serbia produced. The Germans set up a puppet government in order to not tie up a large amount of German manpower. The first puppet government was the short-lived Commissioner Government, established on 30 May 1941, under the leadership of Milan Aćimović. He was an anti-communist and had been in contact with the German police before the war. His cabinet consisted of nine members, many of whom were former cabinet members under the Kingdom of Yugoslavia and were known to be pro-German. It lacked any real power and was no more than an instrument of the Germans. As communist partisans began an 