The "need to protect" the Ukrainian and Belarusian majority populations was used as a pretext for Soviet invasion of Eastern Poland (including Western Ukraine and Belarus) carried out in the wake of Poland's dismemberment under the Nazi invasion with Warsaw being besieged and Poland's government being in the process of evacuation. The total area, including the area given to Lithuania, was , with a population of 13.299 million, of which 5.274 million were ethnic Poles and 1.109 million were Jews. An additional 138,000 ethnic Poles and 198,000 Jews fled the German occupied zone and became refugees in the Soviet occupied region. The borders were finalized in the September 28 German–Soviet Frontier Treaty, most of whose contents were kept secret.