The war broke out in 1805–1806 against the background of the Napoleonic Wars. In 1806, Sultan Selim III, encouraged by the Russian defeat at Austerlitz and advised by the French Empire, deposed the pro-Russian Constantine Ypsilantis as Hospodar of the Principality of Wallachia and Alexander Mourousis as Hospodar of Moldavia, both Ottoman vassal states. Simultaneously, the French Empire occupied Dalmatia and threatened to penetrate the Danubian principalities at any time. In order to safeguard the Russian border against a possible French attack, a 40,000-strong Russian contingent advanced into Moldavia and Wallachia. The Sultan reacted by blocking the Dardanelles to Russian ships and declared war on Russia. According to the Treaty, the Ottoman Empire ceded the eastern half of Moldavia to Russia (which renamed the territory as Bessarabia), although it had committed to protecting that region. Russia became a new power in the lower Danube area, and had an economically, diplomatically, and militarily profitable frontier. The treaty was approved by Alexander I of Russia on June 11, some 13 days before Napoleon's invasion of Russia began. The commanders were able to get many of the Russian soldiers in the Balkans back to the western areas before the expected attack of Napoleon.