In June 1939, Rowecki commanded the Warsaw Armored-Motorized Brigade, charged with defense of the middle Vistula, but he could not organize it in time to defend effectively against the German invasion of 1 September. After Warsaw capitulated, he received orders from General Julisz Karol Rommel to lead the Sluzba Zwyciestwu Polski (Service for Victory in Poland, later renamed the Zwiazek Walki Zbrojnej, or Union for Armed Struggle, and then the Armia Krajowa, or Home Army, in 1942)—an underground force created by the Polish government-in-exile to disrupt the occupying Germans. Rowecki unified nearly all underground elements in Poland under his Armia Krajowa and developed it into a powerful resistance movement. His successful coordination of sabotage, intelligence gathering, and disruption of German lines of communication and war production earned him the pseudonym "Grot" (Arrowhead) and promotion to brigadier general.
Rowecki kept underground operations sporadic while waiting for the occupying German forces to weaken before launching a full uprising. Gestapo agents arrested him on 30 June 1943, tortured him, and sent him to the Sachsenhausen concentration camp. He was murdered there on direct orders from Heinrich Himmler on the first day of the Warsaw Rising, 1 August 1944. Bradford Wineman
Korbonski, Stefan. The Polish Underground State: A Guide to the Underground, 1939–1945. New York: Hippocrene Books, 1981.; Szarota, Tomasz. Stefan Rowecki. Warsaw: Panstewowe Wydawn, 1983.