That is the Crimean War, which lasted from October 1853 to February 1856.
Balaklava from Guard’s Hill, Crimea, 1855, Roger Fenton, The Royal Photographic Society Collection © National Media Museum, Bradford / SSPL. Creative Commons BY-NC-SA
The Crimean War of the 1850s was caused when Russia moved southwards into Crimea to gain control of the warm water ports of the Black Sea which didn’t freeze over in the winter, and were essential if Russia was to build a strong navy and benefit from all year round international trade.
The Ukraine crisis echoes Fenton’s early war photography in Crimea.