Despite a Polish victory at the Battle of Szack (the Soviets later executed all the officers and NCOs they had captured), the Red Army reached the line of rivers Narew, Bug, Vistula and San by 28 September, in many cases meeting German units advancing from the other direction. Polish defenders on the Hel Peninsula on the shore of the Baltic Sea held out until 2 October. The last operational unit of the Polish Army, General Franciszek Kleeberg's "Samodzielna Grupa Operacyjna "Polesie"", surrendered after the four-day Battle of Kock near Lublin on 6 October, marking the end of the September Campaign.