The Polish unit was tasked with defending the Narew river line with important bridgeheads at Różan, Ostrołęka, Osowiec Fortress, Nowogród, Łomża and Wizna, and to cover the right flank of the Modlin Army.

[1] The cavalry was tasked with organising delaying actions along the Polish-German border and the Biebrza River further to the north-east from Łomża.

Although outdated and unsuitable for modern warfare, the forts in Piątnica were upgraded with trenches, barbed wire obstacles, chevaux de frise and 12 reinforced concrete bunkers in 1939.

[3] Similarly the southern bank around Łomża was reinforced with 9 more bunkers, though shortly before the war their machine guns were moved to Piątnica.

[4] Initially the Germans did not attack from East Prussia during the first week of World War II the front of SGO Narew was mostly stable.

After 3 September the town of Łomża was bombarded by the Luftwaffe several times and was set on fire, but the Polish forces suffered only negligible losses.

[5] On 7 September, shortly after noon, the 21st Infantry Division of XXI Army Corps (Germany) (under Gen. Nikolaus von Falkenhorst) reached the forward outposts of the Polish positions in front of Łomża.

In the evening the 21st Division tried to outflank the Łomża bridgehead by fording the Narew, but the Germans were pushed back across the river by vigorous Polish counterattack.

[3] Despite three days of repeated German attacks and significant losses (roughly 30% in dead and wounded), Polish morale was still high.

The following day the German forces captured Łomża unopposed and on 29 September the town was handed over to their Soviet allies.