The Russo-Turkish War of 1806-1812 was fought between the Russian Empire and the Ottoman Empire from 1806 to 1812, resulting in the Russian conquest of Bessarabia.
In 1806, following the Russian defeat at the Battle of Austerlitz, Sultan Selim III deposed the pro-Russian Constantine Ypsilantis as Prince of Wallachia and Alexander Mourousis as Prince of Moldavia. Simultaneously, the French Empire occupied Dalmatia and threatened to penetrate the Danubian principalities at any time. A 40,000-strong Russian army was sent into Moldavia and Wallachia to protect the Russian border, causing the Sultan to block the Dardanelles to Russian ships and declare war on Russia.
Initially, Tsar Alexander I of Russia was reluctant to concentrate large forces against the Ottoman Empire while his relations with Napoleonic France were still uncertain and the main part of his army was occupied fighting against Napoleon in Prussia. A massive Ottoman offensive aimed at Romanian-occupied Bucharest was checked at Obilesti on 2 June 1807, while a 7,000-strong Russian army destroyed a 20,000-strong Turkish army at the Battle of Arpachai in Armenia on 18 June. In the meantime, the Imperial Russian Navy blockaded the Dardanelles and defeated the Ottoman fleet at the Battle of the Dardanelles, after which Selim III was deposed and murdered. The following month, the Ottoman fleet was destroyed at the Battle of Athos, establishing Russian naval supremacy.
The Peace of Tilsit with France in 1807 emboldened Alexander to transfer more Russian soldiers from Prussia to Bessarabia. The southern army was augmented to 80,000, and Prince Pyotr Bagration took command in 1809. Bagration besieged Silistra before retreating as a 50,000-strong Turkish army approached the city. In 1810, the Russians defeated the Turkish reinforcements headed for Silistra, and the city surrendered on 30 May 1810. The Russians suffered heavy losses during a failed attack on Shumla (Shumen, Bulgaria) and in the storming of Rousse (Ruse, Bulgaria) on the Danube, but the Russians surprised and routed a huge Turkish detachment at the 26 August Battle of Batin and crushed another Russian army at Vidin on 26 October. The Russians still failed to achieve any important victories that would force the Ottomans to end the war, and the straining of relations with France forced Russia to end the war quickly to concentrate on dealing with Napoleon. Alexander appointed his hated general Mikhail Kutuzov to deliver the decisive blow, which he achieved at Ruscuk on 22 June 1811 and at the Battle of Slobozia, where the Turks suffered 36,000 casualties. Peace negotiations ensued, and the 28 May 1812 Treaty of Bucharest ended the war. The Caucasus front had ended in stalemate, but the Ottomans ceded the eastern half of Moldavia (Bessarabia) to the Russians, making Russia a new power in the lower Danube. Turkey regained Poti, Anapa, and Akhalkalali in Transcaucasia, but the Sultan accepted the Russian annexation of Imereti in 1810. 13 days after the Russo-Turkish peace, the French invasion of Russia began.