Because it was mainly Europe that was Christian. Asia was for example mostly Buddhist, Confucian, and Hindu. The Middle East and Northern Africa was Islamic. The rest of the world was influenced by Europe and it’s Christianity.
Do you mean the conflict between 1853 and 1853?
All the parties in this conflict were:
The Ottoman Empire (today's Turkey), which had an alliance with France, United Kingdom and the Kingdom of Sardinia (which was only part of Italy in 1861).
Their opponent was Russia.
These changes impacted the way we teach and see history for years to come. In events such as the Murder of Nanking (committed by Japan), the horrors committed in the Polish termination camp (Auschwitz), and the Holocaust Twin experiment, many people were murdered and faced many cruelties. Now we study the works of Hitler, Stalin, and many others like them with caution. Though some people still believe that what Hitler did was correct (neo-nazis) or that the entire holocaust was completely made up (this is a false statement), it was a real event and had cause many people pain, and lots of people lost loved ones.
