|"Is this all real? Or has this been happening inside my head?"
The topic of this article is of a real-life subject that has been mentioned "in-universe" in a canon source. The Harry Potter Wiki is written from the perspective that all information presented in canon is true (e.g., Hogwarts really exists), and, as such, details contained in this article may differ from real world facts.
The Crimean War was a Muggle military conflict fought from 1853 to 1856, between Russia and an alliance of France, Britain, the Ottoman Empire and Sardinia, and which immediate cause involved the rights of Christian minorities in the Holy Land.