The Crimean War was a military conflict between the allied forces of the Ottoman Empire, United Kingdom, French Empire and the Kingdom of Sardinia against the Russian Empire, fought from October 1853 to March 1856. Although the immediate cause of war was the violent dispute between the Catholic and Orthodox Church over the preeminence in Jerusalem, the root cause of the war was the struggle for supremacy over the Black Sea and the strategically important Dardanelles and Bosphorus straits in Turkey. Armed hostilities began with the Russian occupation of Danubian Principalities of Moldavia and Wallachia in June 1853. Although, at first, the United Kingdom and the French Empire engaged in the conflict by exaggerating the protection of the Ottoman Empire from the Russian offensive, during the spring of 1854. the conflict escalated into an open war between the Allied forces and the Russian Empire. The war was fought on several battlefields, with the most important campaign fought on the Crimean Peninsula where the Allied forces set out to destroy the Russian naval base at Sevastopol. Even though the strategic plan foresaw the rapid destruction of Sevastopol, due to the unpreparedness of the army for winter conditions, incompetent military command and an outbreak of contagious diseases, the Crimean war became one of the most gruesome episodes in modern history. Sevastopol fell after an eleven-month siege, which made way for diplomatic negotiations and a peace treaty in Paris in March 1856.