Crimean War - Britain declares war on Russia.

Russian expansionism included exploiting the decline of the Ottoman Empire in order to gain territories affording access to the Mediterranean and Indian Ocean. France had been backing the Roman Catholic Church's claims to be the guardians of the holy places in Palestine. When the Ottomans, under French diplomatic and military pressure, removed the keys of the Church of the Nativity from the Orthodox Church and passed their control to the Roman Catholic Church, the Czar reacted. Russia, under the pretext of protecting Orthodox rights, invaded the Moldavia and Wallachia principalities of the Ottoman Empire in a move designed to pressurise the Ottomans into reversing their decision. France declared war on Russia on 27 March 1854. The British, always opposed to Russian ambitions in the 'Great Game', declared war on Russia on 28 March 1854.