Leo Tolstoy began publishing War and Peace in serialized form in 1865.
The novel first appeared in the Russian magazine Russky Vestnik, or The Russian Messenger. Tolstoy continued revising the work as it was published, and the completed novel appeared in book form in 1869. Its final structure combines fictional families with historical figures and events surrounding Napoleon’s invasion of Russia in 1812.
The early serialized version differed from the later book. Tolstoy changed passages, reorganized material, and developed the philosophical sections that discuss history, leadership, and the relationship between individual choices and large social forces.
Readers sometimes give 1869 as the publication year because that is the date associated with the completed book edition. The more precise answer to a question about serialized publication is 1865, when the novel began appearing in Russky Vestnik.