Crimean War

The Crimean War (1853–1856), also called the Eastern War (), was fought between the Russian Empire against the French Empire, the United Kingdom, the Kingdom of Sardinia and the Ottoman Empire. Most of the fighting, including the Battle of Balaclava, happened in Crimea, but some of it was what is now western Turkey and around the Baltic Sea. 
The Crimean War is sometimes called the first "modern" war since its weaponry and tactics were used for the first time and affected all later wars. It was also the first war to use a telegraph to give information to a newspaper quickly.
Background.
The Ottoman Empire was declining by the mid-1800s. The war started after the Ottoman Empire decided that France, not Russia, had the right to protect Christians in the Holy Land near the area of modern-day Israel. 
Russia sent an army to take part of Ottoman Romania and so the British and the French allies sent an army and a navy to help the Ottomans. When the allies got to their camp in Gallipoli, Russia retreated and so the allies decided instead to take back Crimea, where Russia had its naval base. Russia had taken Crimea from the Ottoman Empire in an earlier war.
Results.
The Allies won the war in Crimea but gave it back to Russia in return for Russia giving back other places and promising not to have a navy on the Black Sea. 
The Crimean War was a very important point in the history of warfare since new weapons were used. It was also the first war to be reported by the press via photography and journalists. Another very important factor was that it was the first war with real field hospitals, which were started by Florence Nightingale.
After it lost the war, Russia decided to make changes, including increasing its development of weaponry and ending serfdom in 1861.