In the Second Polish Republic, the village of Bełżec was situated between the two major cities in the southeastern part of the country including Lublin northwest of Bełżec, and Lwów to the southeast (, now Lviv, Ukraine) with the largest Jewish populations in the region. Bełżec fell within the German zone of occupation in accordance with the German-Soviet Pact against Poland. Originally, the Jewish forced labour was brought into the area in April 1940 for the construction of military defence facilities of the German strategic plan codenamed Operation Otto against the Soviet advance beyond their common frontier following the Soviet invasion of 1939.&lt;ref name="M/MPwB"&gt;&lt;/ref&gt;