France: Napoleon III
Ottoman Empire: Abdulmecid I
United Kingdom: Earl of Aberdeen
Sardinia: Victor Emmanuel II
Russia: Nicholas I
The main cause of the war was Russian expansion in Southern Europe. The Ottoman Empire was the "Sick man of Europe", and had been slowly declining over the past few years. Russia had been taking advantage of the Ottoman Empire's decline and was expanding south. France did not want Russia to take advantage of the Ottoman Empire because of Russia's plans for the Holy Land. If they ever took over the Holy Land, which they didn't, Russia planned to promote the rights of the Orthodox Christian minority there; France wanted the rights of the Catholic minority to be promoted. The war started between the Ottoman Empire and Russia because the Ottomans wanted to stop Russian expansion in Southern Europe. France got involved on the side of the Ottomans to make sure Russia didn't give Orthodox Christians in the Holy Land any extra rights at the expense of the Catholics there, and the UK and Sardinia got involved because they were aligned with France.
As its name would suggest, most of the fighting in this war happened in or around the Crimean Peninsula. Russia opened up the fighting in the Black Sea by using their naval base in Sevastopol to launch a naval invasion of the Ottoman Empire. In the Battle of Sinop, an Ottoman naval patrol force that was protecting the sea port of Anatolia, Ottoman Empire was completely annihilated by the Russian Black Sea Fleet. The Allies struck back by bombarding the Odessa harbor. The Allies began their Crimean Campaign, a naval invasion of the Crimean Peninsula, in September 1854 when Allied ships landed on the southwestern coast of Crimea. The goal of the Crimean Campaign was to capture Sevastopol, the naval base that Russia had previously launched their invasion of the Ottoman Empire from. Needing extra help to fend off the Allies, Russia evacuated their forces from Wallachia and Moldavia, two places that Russia had been occupying at the start of the war, and brought them to Crimea. The Allies began the Siege of Sevastopol in October 1854. After a multitude of bombardments, the city was captured by the Allies. After that, the Allies captured the rest of Crimea. At this point, both sides were exhausted, and the fighting in Crimea ended. The Allies laid siege to Petropavlovsk, a Russian city in the far east, but suffered huge causalities and ultimately left.
End of the war & lasting effects
The war ended with an Allied victory in 1856 with the signing of the Treaty of Paris. The treaty established that the Black Sea was "Neutral territory" and no warships allowed there. Sevastopol and the rest of Crimea was returned to Russia. One of the effects of this was the Russian dominance in the Black Sea ended for a while, though it would ultimately return. A long term effect of the war was that Russia now felt a greater need to protect the Crimean Peninsula. Russia had previously thought that since they were the only navy in the Black Sea, that no one could touch Crimea; however, this war proved otherwise. Another provision of the treaty was that now France was the only country that was allowed to protect Christians in the Ottoman Empire. The Ottoman Empire was also able to stop its decline for a short time by being on the winning side of this war. The effects of this war war can be seen even today; in 2014 Russia annexed Crimea, a move that will help Russia retain its naval dominance in the Black Sea, which they regained sometime after the Soviet Union was established.