The combat of Ostrolenka (16 February 1807) was a minor French victory won on the right flank of their long front in Poland, and ended a Russian attempt to push the French back in the south.
After their unsuccessful attempt to win a decisive victory at Pultusk (26 December 1806) most of the French army went into winter quarters to the north and north-east of Warsaw. To the left Bernadotte was posted towards the Baltic coast, with Ney linking his corps with the rest of the army. In January 1807 the main Russian army, under General Bennigsen, moved north and then turned west in an attempt to defeat the isolated corps of Marshal Bernadotte, on the extreme left of the French line. Napoleon responded by leading most of his army north at the start of the campaign that ended at Elyau (7-8 February 1807).
Both sides left a holding force in the south. On the French side General Savary was given command of V Corps, made up of Suchet's and Gazan's infantry divisions and Becker's dragoon division, a total of around 18,000 men. Oudinot's grenadier division was also ordered to join Savary, and arrived in time to take part in the fighting at Ostrolenka.
The Russians left two divisions from the Army of Moldavia in the area between the River Bug and the River Narew, under the command of General Essen.
Savary had quite complex orders. If Essen had a weak force at Nur, on the Bug, then Savary was to attack. If the Russians had more men then Savery was to defend Brok, further west on the Bug and Ostrolenka, north of Brok on the Narew River, with cavalry, while his main forces were posted at Pultusk, with orders to guard the right (west and north) bank of the Narew from Sierock (Serock, thirteen miles to the south of Pultusk, where the Narew flows into the Bug) north to the Omulew River, which flows into the Narew close to Ostrolenka, and the River Bug from Sierock east to the Austrian border. He was also to strengthen the bridgehead at Pultusk and build a bridge at Sierock.
Savary didn’t entirely obey his orders. He found his men short of supplies, and decided to move his main force to Ostrolenka. While moving north he captured a copy of orders from Bennigsen to Essen, who had been ordered to go onto the offensive. The Russians sent 4,000-5,000 men onto the right bank of the Narew and advanced towards Ostrolenka, hoping to turn Savary's left flank.
Savary decided to go onto the offensive himself. Three brigades were left at Ostrolenka, on the left (east) bank of the river, commanded by General Reille. They were covered by artillery batteries posted on the opposite side of the river. On 16 February Savary led the rest of his force north along the right bank of the river, heading towards Essen's attacking force.
Gazan's division led the advance on the right bank of the river. His men ran into the advancing Russians as they were passing between two woods. The Russians were unable to deploy and were pushed back for five miles.
At the same time another Russian force was advancing down the left bank of the river towards Ostrolenka. This force drove Reille's brigades back into the town, but the artillery fire across the river disrupted the Russian attack. Savary gathered Suchet's division, which was also on the right bank and part of Oudinot's grenadiers and crossed the river into Ostrolenka.
The French advanced out of the town with Oudinot and the cavalry on the left, closes to the river. Suchet's division was in the centre and Campana's brigade from Gazan's division was on the right. The French attacked and defeated Essen's men, inflicting around 1,000 casualties and capturing seven guns.
In the aftermath of this battle both sides went into winter quarters. Savary was soon replaced by Marshal Massena, who had been summoned from Italy, and the French position was based around large fortified camps.