Complex sentence: Rauschning claimed that before World War I about 1,200,000 Germans had lived in these districts and that there only 350,000 were left in 1929; he concluded that more than 800,000 had been expelled from their homes l.c.
Split into simpler sentences: Rauschning claimed that before World War I, about 1 200 000 Germans had lived in these districts and that there was only 350 000 left in 1929. Therefore he concluded that more than 800 000 had been expelled from their homes l.c.