After their country was invaded in 1939 on two fronts, by both German and Soviet forces, those who lived in occupied Poland throughout the Second World War endured some of the most appalling living conditions and became the victims of the most horrific war crimes of the Holocaust. From the ghetto established in Warsaw by the Germans in 1940, to the horrifying extermination camps set up at sites like Treblinka later in the war, historian Alex Richie tells the harrowing story of occupied Poland in World War Two.