Troop concentrations became the main targets after this until the Polish surrender.[2] II./KG 4 also supported 10.Armee over Kutno in mid September. After the campaign the unit began training in night flying and began to lay mines of the Norwegian coast in January 1940, in preparation for the Norwegian Campaign. III./KG 4 participated in the Battle of the Bzura in which the Polish Army was surrounded and destroyed (largely by the Luftwaffe).[3]