The Fifth Column-a minority German population living inside Poland-aided the German invasion in September, 1939. This report published by the Polish Ministry of Information in 1940 details the treacheries of Germans on their Polish neighbors. As German troops crossed the Polish border on September 1, Fifth Columnists were ready, marking targets for German pilots, spreading false information to cause panic, spying on Polish troop movements, firing on Polish soldiers, sabotaging Polish facilities, and executing Polish patriots. Most fascinating is how well coordinated the activities were between the Wehrmacht and the Fifth Column, which had been carefully trained and well equipped months before the invasion. Under the very noses of their Polish neighbors, Germans living in Poland had buried stockpiles of fuel and ammunition, concealed their insignias under their regular clothes and even armed their Lutheran church towers as strategic sniper positions. As the German occupation of Poland began its bloody rule of terror and the war spread to other countries, the truth of the Fifth Column was buried under ever more horrible news. Still, it is an important lesson in national security and the possible enemy within, hiding in plain sight and waiting to strike at the right moment.