It was in April 1941, after having finished The Betrothal in a Nunnery that Prokofiev thought of writing an opera based on Tolstoy's novel War and Peace. Two months later, the Nazis broke the "Molotov-Ribbentropy" pact with their invasion of the USSR. Thus, the war had already begun when Prokofiev was developing his libretto with the help of his second wife Myra Mendelssohn and the participation of Eisenstein.
Apart from reading Tolstoy, he immersed himself in historical documents and went as far as studying the military songs and various proverbs of the Napoleonic era.
"The pages of the novel describing the Russian people's struggle against Napoleon's armies became particularly current and I clearly felt that they were to serve as the basis of the opera," he states in his autobiography.
In adapting Tolstoy's epic story, the librettists had to make drastic cuts but remained faithful to the spirit of the novel. The first Act - Peace - i.e., the first seven scenes, chronicles the lives and intrigues of the characters thus giving Prokofiev the pportunity to compose, in a style reminiscent of Tchaikovsky, music of pure elegance, interspersed with valses and vigorous rhythms, that was meant to depict the frivolity of Moscow's high society before the French invasion.
In contrast, the second Act - War - , relates historical events involving characters from the first Act caught in the whirlwind of a collective drama. This evocation of war atrocities is much more modern in its dislocated dramatic design as well as its musical flirtation with dissonances. The magnitude and number of characters (seventy two!) of "War and Peace" and the means required by its production make it one of the most difficult works to bring to stage.