Upon the defeat of the
Third Reich in
World War II, the victorious
Allied powers asserted their authority over all territory of the
German Reich which lay west of the
Oder–Neisse line, having formally abolished the government of
Adolf Hitler (see
1945 Berlin Declaration). The four powers divided Germany into four
occupation zones for administrative purposes, into what is collectively known now as
Allied-occupied Germany . This division was ratified at the
Potsdam Conference (17 July to 2 August 1945). In Autumn 1944 the United States, United Kingdom, and
Soviet Union had agreed on the zones by the
London Protocol. The powers approved the eventual detachment of much of the German eastern territories, lying east of the Oder-Neisse line, from Germany; the contemplated Final German Peace Treaty would determine the Polish-German and USSR-Polish border lines for the former German territories. The Final German Peace Treaty would result in the "shifting westward" of Poland's borders back to approximately as they were before 1722. In the closing weeks of fighting in Europe, United States forces had pushed beyond the agreed boundaries for the future zones of occupation, in some places by as much as . The so-called
line of contact between Soviet and
American forces at the end of hostilities, mostly lying eastward of the July 1945-established
inner German border was temporary. After two months in which they had held areas that had been assigned to the Soviet zone, U.S. forces withdrew in the first days of July 1945. Some have concluded that this was a crucial move that persuaded the Soviet Union to allow American, British, and French forces into their designated sectors in Berlin, which occurred at roughly the same time (July 1945), although the need for intelligence gathering (see
Operation Paperclip) may also have been a factor.