claim: Cordilleran Ice Sheet periodically covered large parts of Africa.
evidence: The Polish Post Office -LRB- Poczta Polska -RRB- in the Free City of Danzig -LRB- Gdansk -RRB- was created in 1920 and operated until the German invasion of Poland that marked the beginning of the World War II .. Poczta Polska. Poczta Polska. Free City of Danzig. Free City of Danzig. German invasion of Poland. German invasion of Poland. World War II. World War II