The Crimean War is a military conflict fought from October 1853 to February 1856 in which the Russian Empire loses to an alliance of the Ottoman Empire, France, Britain and Sardinia.

The immediate cause involves the rights of Christian minorities in the Holy Land, which is a part of the Ottoman Empire.

The French promote the rights of Roman Catholics, while Russia promotes those of the Eastern Orthodox Church.

The longer-term causes involve the decline of the Ottoman Empire and the unwillingness of Britain and France to allow Russia to gain territory and power at Ottoman expense.

It has widely been noted that the causes, in one case involving an argument over a key, have never revealed a "greater confusion of purpose", yet led to a war noted for its "notoriously incompetent international butchery".

While the churches work out their differences and come to an agreement, Nicholas I of Russia and the French Emperor Napoleon III refuse to back down.

Nicholas issues an ultimatum that the Orthodox subjects of the Ottoman Empire be placed under his protection.

Britain attempts to mediate and arranges a compromise that Nicholas agrees to.

When the Ottomans demand changes, Nicholas refuses and prepares for war.

Having obtained promises of support from France and Britain, the Ottomans declare war on Russia in October 1853.

The war starts in the Balkans in July 1853, when Russian troops occupy the Danubian Principalities (part of modern Romania), which are under Ottoman suzerainty, then begin to cross the Danube.

Led by Omar Pasha, the Ottomans fight a strong defensive campaign and stop  the advance at Silistra.

A separate action on the fort town of Kars in eastern Anatolia leads to a siege, and a Turkish attempt to reinforce the garrison is destroyed by a Russian fleet at Sinop.

Fearing an Ottoman collapse, France and Britain rush forces to Gallipoli.

They then move north to Varna in June 1854, arriving just in time for the Russians to abandon Silistra.

Aside from a minor skirmish at Köstence (today Constanța), there is little for the allies to do.

Karl Marx quips, "there they are, the French doing nothing and the British helping them as fast as possible".

Frustrated by the wasted effort, and with demands for action from their citizens, the allied force decide to attack Russia's main naval base in the Black Sea at Sevastopol on the Crimean peninsula.

After extended preparations, the forces land on the peninsula in September 1854 and march their way to a point south of Sevastopol after the successful Battle of the Alma.

The Russians counterattack on October 25 in what becomes the Battle of Balaclava and are repulsed, but at the cost of seriously depleting the British Army forces.

A second counterattack, at Inkerman, ends in stalemate.

The front settles into a siege and leads to brutal conditions for troops on both sides.

Smaller actions are carried out in the Baltic, the Caucasus, the White Sea, and in the North Pacific.

Sevastopol falls after eleven months, and neutral countries begin to join the Allied cause

Isolated and facing a bleak prospect of invasion from the west if the war continued, Russia sues for peace in March 1856.

This is welcomed by France and Britain, as the conflict is growing unpopular at home.

The war is ended by the Treaty of Paris, signed on March 30, 1856.

Russia is forbidden to host warships in the Black Sea.

The Ottoman vassal states of Wallachia and Moldavia become largely independent.

Christians there are granted a degree of official equality, and the Orthodox Church regains control of the Christian churches in dispute.

The Crimean War is one of the first conflicts to use modern technologies such as explosive naval shells, railways, and telegraphs.

The war is one of the first to be documented extensively in written reports and photographs.

As the legend of the "Charge of the Light Brigade" demonstrates, the war quickly becomes an iconic symbol of logistical, medical and tactical failures and mismanagement.

The reaction in the UK is a demand for professionalisation, most famously achieved by Florence Nightingale, who gains worldwide attention for pioneering modern nursing while treating the wounded.

The Crimean War proves to be the moment of truth for Nikolaevan Russia

Its humiliating outcome forces Russia’s educated elites to identify the Empire’s problems and recognize the need for fundamental transformations aimed at modernizing and restoring Russia’s position in the ranks of European powers.

Historians have studied the role of the Crimean War as a catalyst for the reforms of Russia’s social institutions: serfdom, justice, local self-government, education, and military service.

More recently, scholars have also turned their attention to the impact of the Crimean War on the development of Russian nationalistic discourse.