The siege of Pleven, was fought by the joint army of Russian Empire and Kingdom of Romania against the Ottoman Empire. After the Russian army crossed the Danube at Svishtov, it began advancing towards the centre of modern Bulgaria, with the aim of crossing the Balkan Mountains to Constantinople, avoiding the fortified Turkish fortresses on the Black Sea coast. The Ottoman army led by Osman Pasha, returning from Serbia after a conflict with that country, was massed in the fortified city of Pleven, a city surrounded by numerous redoubts, located at an important road intersection.
After two unsuccessful assaults, in which he lost valuable troops, the commander of the Russian troops on the Balkan front, Grand Duke Nicholas of Russia insisted by telegram the help of his Romanian ally King Carol I. King Carol I crossed the Danube with the Romanian Army and was placed in command of the Russian-Romanian troops. He decided not to make any more assaults, but to besiege the city, cutting off the food and ammunition supply routes.
At the beginning of the siege, the Russian-Romanian army managed to conquer several redoubts around Pleven, keeping in the long run only the Grivița redoubt. The siege, which began in July 1877, did not end until December of the same year, when Osman Pasha tried unsuccessfully to force the siege to break and was wounded. Finally, Osman Pasha received the delegation led by General Mihail Cerchez and accepted the conditions of capitulation offered by him. The Russian–Romanian victory on 10 December 1877 was decisive for the outcome of the war and the Liberation of Bulgaria. Following the battle, the Russian armies were able to advance and forcefully attack the Shipka Pass, succeeding in defeating the Ottoman defense and opening their way to Constantinople.