At the beginning of the Russo-Turkish War, he commanded the 12th Army Corps to crossed the Danube, the Army Corps was later incorporated into the Ruschuk Detachment (the Eastern Detachment), for which he was appointed chief of staff of it, commanded by the tsesarevich, the future emperor Alexander III, whom he would become close friend with after the war. The Ruschuk Detachment was exceptionally powerful among other Russian units. It was composed of the 12th and the 13th Army Corps, 49 battalions, 19 Cossack divisions and 224 guns. The task of the detachment was to take the small Ottoman towns of Ruse and Nikopol, but when they arrived, they were attacked by the Ottomans and as a result, they went fully defensive, but they could still break through the Ottomans and won significant victories. Later on the Ottomans attempted to launch an offensive between the villages of Gorsko Ablanovo and Katselovo, but the Russians repulsed them, inflicting huge casualties on the Ottoman. After this decisive battle, the Ottomans did not dare to launch any offensive for a period of time. After some time, the Ottoman high command made a decision to attack the right flank and the center of the Ruschuk Detachment with 28 squadrons and 84 guns, in order to encircle the detachment from the rear. But the plan was later unravelled by Vannovsky, and the Russian Army soon went to defensive position. On 9 September, when the Ottomans attacked, they got counter-attacked by the Russians, inflicting huge casualties on the Ottomans. This victory was very important for the breakthrough in Plevna because the rear of the army was now protected from being attacked.