guderian was informed of hitler's decision to invade poland through his superior, günther von kluge, commander of 4th army, on 22 august 1939. he was ordered to pomerania, where 4th army and with it xix army corps were stationed, to join the "befestigungsstab pommern" ('fortification staff pomerania') and to officially construct military fortifications against a supposed polish attack. walther nehring was assigned to be xix army corps' chief of staff.