The Siege of Plevna, or Siege of Pleven, was a major battle of the Russo-Turkish War of 1877–1878, fought by the joint army of Russia and Romania against the Ottoman Empire. The Ottoman defense held up the main Russian advance southwards into Bulgaria for five months, encouraging other great powers actively to support the Ottoman cause. Eventually, superior Russian and Romanian numbers forced the garrison to capitulate. The Russian-Romanian victory on 10 December 1877 was decisive for the outcome of the war and the Liberation of Bulgaria. https://en.wikipedia.org/wiki/Siege_of_Plevna
