The most accurate point of comparison between the situations leading up to the invasions of China and Poland is:
Japan and Germany invaded other countries before invading China and Poland.
Both Japan and Germany had aggressive expansionist policies that led them to invade other nations prior to their invasions of China and Poland. Japan invaded Manchuria in 1931 and further expanded into China in the mid-1930s, while Germany annexed Austria and invaded Czechoslovakia before attacking Poland in 1939. This pattern of earlier aggressions set the stage for their respective invasions of China and Poland.