The Observational Army guarded the borders of the Russian Empire from Austria and the Duchy of Warsaw in modern territories of the south of Belarus and the north-west of Ukraine.

[4] With the outbreak of the war, the Austrians covered the right flank of Napoleon from the Russian Third Army, stationing the border garrisons along Brest—Kobryn—Pinsk line with a length of 170 kilometers.

[4] Tormasov selected 5 cavalry regiments (mostly dragoons) to protect the borders of Russian Empire from the Duchy of Warsaw, that was allied to Napoleon.

Then he pulled the available forces to Kovel, dividing the army into 5 parts: On 24 July, General Scherbatov occupied Brest, knocking out 2 enemy squadrons from the corps of Reynier.

[4] Kobryn was occupied by a 5,000-strong Saxon brigade commanded by Major General Klengel from the 22nd Infantry Division of the Reynier corps.

[4] Lambert in the west early in the morning attacked the enemy with the forces of irregular cavalry, trying to entice the Saxons into the open field.

Tormasov ordered General Chaplits to bypass Kobryn from the east with the vanguard, leaving a little cavalry to block the soldiers of Klengel, who had settled in the buildings on the southern outskirts.

Lambert managed to bring down the Saxons' cover from the road, but they were entrenched in urban buildings, barring the way to the city from the west.

Prince Vyazemsky wrote the impressions of the battle in the diary the next day: All in flame, wives, girls in only shirts, children, all fleeing and seeking salvation; the battle in the fire, the rapid movement of troops, scattered enemy transporters, roaring and running cattle through the field, the dust eclipsed the sun, horror everywhere.

By noon the battle was over, the surviving Saxons led by General Klengel were driven into the half-ruined Kobryn castles (part of the gift of Catherine II to count Alexander Suvorov) and surrendered.

[6] On the day of the defeat of the Saxon brigade in Kobryn in the main direction, the 1st Russian army retreated from Napoleon forces to Smolensk after heavy rearguard battles near Vitebsk.