Operational Group (, abbreviated GO) was the highest level of tactical division of the Polish Army before and during World War II and the invasion of Poland. It was corps-sized, although various Operational Groups varied in size. Operational groups first appeared in Polish tactical scheme during the Polish-Bolshevik War, most probably under the influence of French Military Mission to Poland. After the war they were dissolved. Prior to World War II, the operational groups were recreated. Initially, in March 1939, they consisted only of staffs formed around existing corps commands. According to the Polish mobilization scheme, they were to become mobile reserves of the Polish armies and other major strategic-scale units. One of such groups, the Kutno Operational Group, was planned but never created. Also, in the autumn of 1938, the Independent Operational Group Silesia was created with the purpose of capturing Zaolzie from Czechoslovakia. Some groups were formed during the final mobilization of late August 1939, others were formed during the war as strategic considerations necessitated. Most were attached to armies, several however were independent. Independent Operational Groups Independent Operational Group "Polesie" (Samodzielna Grupa Operacyjna Polesie) under gen. Franciszek Kleeberg. Created around September 9th-11th. Independent Operational Group "Narew" (Samodzielna Grupa Operacyjna Narew) under gen. Czesław Młot-Fijałkowski. Created on March 23 Operational Group "Wyszków" (Grupa Operacyjna Wyszków) under gen. Wincenty Kowalski. Created on September 1. Operational Group "Grodno" (Grupa Operacyjna Grodno) under gen. Józef Olszyna-Wilczyński. Created in early September; disbanded on September 10 before the battle of Grodno begun; most units moved towards Lwów. Cavalry Operational Group (or Operational Group of Cavalry) Cavalry Operational Group Abraham (Grupa Operacyjna Kawalerii Abraham) under Roman Abraham Cavalry Operational Group Anders (Grupa Operacyjna Kawalerii Anders) under gen. Władysław Anders Cavalry Operational Group No.1 (Grupa Operacyjna Kawalerii Nr 1) Cavalry Operational Group No.2 (Grupa Operacyjna Kawalerii Nr 2) Operational Groups as part of armies Operational Group "Bielsko"" (Grupa Operacyjna Bielsko) under gen. Mieczysław Boruta-Spiechowicz (on September 3 renamed to Operational Group "Boruta") (Grupa Operacyjna Boruta) Operational Group "Czersk" (Grupa Operacyjna Czersk) under gen. Stanisław Grzmot-Skotnicki Operational Group "Koło" (Grupa Operacyjna Koło) under gen. Edmund Knoll-Kownacki (on September 6 renamed to Operational Group "Knoll-Kownacki") (Grupa Operacyjna Knoll-Kownacki) Operational Group "Piotrków" (Grupa Operacyjna Piotrków) under gen. Wiktor Thommée (on September 6 renamed to Operational Group "Thommée") (Grupa Operacyjna Thommée) Southern Operational Group (Południowa Grupa Operacyjna) under gen. Stanisław Skwarczyński Northern Operational Group (Pólnocna Grupa Operacyjna) under gen.