During the halt at Brest-Litovsk General Sacken joined the army from the south, bringing with him about 4000 depôt troops, who appear to have been drafted into the weaker units.
While the Admiral himself remained at Brest, preparing for the march to the Berezina, he sent out detachments to overrun Warsaw and sweep the country towards Minsk. The detachments sent towards Warsaw were supported by Essen III’s division, which, on October 18th, came in contact at Biala with Reynier and was driven back, with a loss of several hundred men and a gun, upon Brest-Litovsk. On the other hand, General Chaplitz on the 20th destroyed the new Lithuanian regiment of Napoleon’s Guard at Slonim, only about 120 men escaping out of 600. Chaplitz’s detachment was supported by Cherbatov’s (formerly Markov’s) division. Eastward of Slonim there were very few invading troops to cover the long line of communications, threatened on the south by Russian forces at Bobruisk and Mozyr. The garrison of Bobruisk was not strong enough to make effective sorties, but the force at Mozyr had been gradually increased to about 12,000 men and over 30 guns. To guard against the menace of this force and to observe Bobruisk, Dombrowski’s infantry division and three regiments of cavalry had been left by Poniatowski in August. Dombrowski’s whole force, even after the junction of some Lithuanian levies, can never have exceeded 9000 men, and was barely sufficient, after garrisoning Mohilev, to observe Bobruisk, much less to oppose any effectual resistance to Ertel. On September 11th a column from Mozyr forced an Austrian detachment to abandon Pinsk, while a second, under Ertel himself, defeated Dombrowski’s Lithuanians on the 15th and threw some reinforcements into Bobruisk. Then, however, he retired to Mozyr.
From Riga on August 7th Essen again made a sortie and captured Schlock, which was then retaken by the Prussians. On the 23rd Essen decided to make a general attack upon the Prussians, who lay observing the city, extended from Schlock to Thomsdorf on the Düna, a distance of 42 miles. A column under Lewis was to make the real attack upon Eckau, while a detachment under Major-General Veliaminov demonstrated towards Mitau, and Rear-Admiral von Müller with a flotilla of sloops attacked Schlock. The Prussian posts at Dahlenkirchen on the Düna were driven back, with some loss, by Lewis, but Veliaminov’s demonstration had no results, though von Müller captured Schlock. On the 26th Grawert, having collected his scattered detachments, drove Lewis back into Riga; and Schlock and Dahlenkirchen were reoccupied. The losses in these actions, combined with sickness, considerably weakened the garrison. On the other hand, they proved that the Prussians were not strong enough even to blockade the place. Macdonald sent a brigade of Grandjean’s division to reinforce them, and prepared to bring up the rest of it at need.
After this both sides lay inactive until September 18th, when there was some more indecisive skirmishing about Schlock. The Prussians were now commanded by Lieutenant-General Yorck, Grawert being invalided. Between the 20th and 22nd, Count Steingell’s corps from Finland, which had landed at Revel on the 10th, entered Riga. It had sustained some losses by shipwreck, and part of the troops were detained by contrary winds, so that Steingell had with him only a little over 10,000 men and 18 guns. Nevertheless, the force in Riga was now over 20,000 strong, and an attempt could be made to execute the Tzar’s orders.
On the 26th accordingly Steingell with his own troops and a division under Lewis moved out upon Dahlenkirchen. It was easily occupied, and on the 27th Steingell advanced upon Eckau, where Yorck had collected several regiments. His superiority in artillery enabled him to hold Steingell in check until the arrival of Lewis, when he retired behind the Aa, abandoning Bausk.
While Steingell was pushing back Yorck, Essen directed a column of 2000 men and 6 guns upon Mitau from Riga, while a flotilla came up the Aa. Essen’s hope was to destroy the siege train, which, however, was not there. He ordered Steingell to support the advance with 3000 men and 6 guns, under Colonel Ekeln. On the 28th Yorck, being not yet joined by Hunerbein’s brigade (Grandjean’s division), ordered General Kleist to abandon Mitau and come to reinforce him. This Kleist did, and on the 29th the Russians occupied the place without opposition. But meanwhile Yorck, reinforced by Kleist and Hunerbein, took the offensive against Steingell’s weakened force and began to drive it back. There was some not very vigorous fighting along the Aa, as the result of which the Prussians gained a foothold on the farther bank.
Hunerbein, coming from the right, had retaken Bausk, and on the 30th Yorck made a general advance, driving Steingell back all along the line. The fighting was not at all severe, Steingell merely gave way deliberately before the advance of Yorck’s now superior columns. On the other hand, Yorck was probably not anxious to do more than his strict military duty required. Steingell retired towards Riga with no serious loss and re-entered the lines on the 2nd of October, Essen at the same time evacuating Mitau. The losses on neither side were heavy.
The result of the action was that Macdonald decided to come himself to the support of Yorck. Leaving a Polish regiment in Dünaburg he marched for Mitau with the rest of Grandjean’s division, but when he arrived the Russians had retreated into Riga. The Marshal increased Hunerbein’s brigade to 8 battalions, rearranged the positions of the troops, and sent Grandjean with one brigade back to Illuxt, near Dünaburg. To draw closer to Riga with his feeble forces was evidently impossible, and week after week wore itself away without any fighting except some occasional skirmishing at the outposts.
After his victory at Polotsk, on August 18th, St. Cyr had been unable to follow in pursuit of Wittgenstein owing to his weakness in cavalry fit for the purpose. Wittgenstein therefore was able to withdraw unmolested behind the Drissa. On the 22nd Wrede made a strong reconnaissance towards Sivokhino, but the Bavarians were repulsed by a detachment under Colonel Vlastov with a loss of about 300 killed and wounded and 150 prisoners.