During the impressive Warsaw Uprising of 1794 Igelström lost control of his eventually defeated forces.
In 1753, Otto entered military service in Russia, participated in the Russo-Turkish War of 1768–1774, having taken Akkerman.
In 1784, he commanded Russian troops in Crimea and took the last Crimean khan Şahin Giray prisoner.
He participated in Russo-Swedish War of 1788–1790 and was involved in a botched battle of Pardakoski–Kärnakoski of 30 April 1790 initiated by Ivan Saltykov.
Paul I of Russia took him into service in the rank of infantry general and appointed the governor-general to Orenburg Governorate in 1797.