The 'Battle of Kobryń' was a battle between German and Polish forces within the context of 'Weiss' (i) (14/18 September 1939).

The forces involved were, on the German side, Generalleutnant Paul Bader’s 2^nd Division (mot.) of General Heinz Guderian’s XIX Corps (mot.) within Generaloberst Fedor von Bock’s Heeresgruppe 'Nord', and on the Polish side. Pułkownik Adam Epler’s 2^nd Reserve Division 'Kobryn' of General brygady Franciszek Kleeberg’s Independent Operational Group 'Polesie'. The battle was fought at the same time as the 'Battle of Brześć Litewski'.

After breaking through the Polish defences in the Battle of Wizna, Guderian’s corps started to make its way towards Brześć, Kowel and Kobryń with the object of cutting the Poland in two and paralysing all Polish attempts to organise a defensive line to the east of the Bug river.

On 14 September, elements of the XIX Corps (mot.) reached the area of Brześć and Kobryń. Brześć was defended by a small force under General brygady Konstanty Plisowski, while Kobryń was defended by Epler’s improvised 60^th Reserve Division. Early in the morning of 14 September, Epler was informed that German forces were entering the area for which his division was responsible. Elements of the XIX Corps, notably part of Generalleutnant Leo Freiherr Geyr von Schweppenburg’s 3^rd Panzerdivision and the whole of Bader’s 2^nd Division (mot.), were advancing rapidly and Epler suspected that the Germans would advance on the towns of Brześć and Kobryń, as well as toward the important railway junction in the village of Żabinka. To probe the German forces, Epler ordered the 2/84^th Regiment to begin a delaying action in the area of Żabinka station and the villages of Tewela and Ogrodniki. At the same time, the 2/83^rd Regiment was instructed to organise a defensive line along the swampy banks of the Trościanica river to cover the eastern flank of the Polish forces in the area of Brześć, some 18.6 miles (30 km) to the west.

On 15 September the 3^rd Panzerdivision encountered and destroyed a column of the 9^th Reserve Light Artillery Depot. However, Epler’s forces were not spotted until a time late in the evening of the day, when they were attacked by German warplanes. On the following day the main force of the XIX Corps (mot.) arrived. The 2/84^th Regiment together with an armoured train organised an ambush and attacked the Germans, who were supported by a battery of artillery. In the six hours of fighting which followed, the Germans were forced to retreat with significant casualties. The Polish battalion seized several tanks and pieces of artillery, but had to burn them for lack of the fuel with which they could otherwise have been evacuated, and then retreated toward the main line of the Polish defences.

At dawn on 17 September, reconnaissance units of the 2^nd Division (mot.) reached the Polish lines. After a short skirmish, the Poles withdrew behind their defensive positions held by the 2/83^rd Regiment. The Germans then tried to outflank the Poles by attacking the cemetery in the village of Chwedkowice, but were repelled with light casualties, mostly to the direct fire of Polish 100-mm (3.94-in) howitzers. The 2^nd Division (mot.) lost three or four armoured cars and was forced to retreat, while the Polish battalion withdrew toward the village of Piaski, where it organised another ambush. In the afternoon the Polish battalion was again attacked by elements of the 2^nd Division (mot.), which was also repelled.

It was on 17 September that the Soviet invasion of Poland from the east started.

Overnight, the Polish forces involved in the 'Battle of Brześć' were withdrawn to the other side of the Bug river and joined the forces of Kleeberg’s Independent Operational Group 'Polesie'. Limited numbers of Polish reinforcements arrived at Kobryń, but the defense of the area had by this time lost much of its strategic significance. Epler decided to defend the area as long as possible and then retreat to the south in the wake of Kleeberg’s forces.

The main battle for Kobryń began on 18 September. Early in the fighting, the Germans managed to capture the Gubernia I and Gubernia II manorial farms, which were protecting the road to Bereza Kartuska and closing the approach to main forces of the Polish division. A Polish counterattack from Kobryń forced the Germans to fall back from one of the manorial farms, but this was later recaptured. Fierce combat broke out near the Queen Bona Canal, but the Germans were unable to seize complete control of Kobryń on 18 September because of the determined Polish resistance, resulting in an impasse.

During the day, Polish patrols and units of the eastern wing of Independent Operational Group 'Polesie' came into contact with advanced units of the Soviet XXIII Corps, advancing from the east, in the area of Łuniniec. Faced with general knowledge of the large-scale Soviet Invasion of Poland debouching from the east and specific reports from units of the Independent Operational Group 'Polesie' as they encountered the Soviet spearhead units, Kleeberg amalgamated all elements of his Independent Operational Group 'Polesie' under his command together with the improvised 60^th Division and withdrew to the south toward the Pinsk marshes in the area of Dywin. The headquarters of the Independent Operational Group 'Polesie' was relocated from Pińsk to Lubieszów.

With the withdrawal of the Polish forces, the 'Battle of Kobryń' came to an end.