The Ballad of War mono-opera (1971) by the outstanding Ukrainian composer-songwriter Oleksandr Bilash, based on The Ballad of Genes poem by Ivan Drach, is studied in the article. It is emphasized that the work of O. Bilash – I. Drach is extremely relevant today, as it reveals the painful and tragic theme of war and its destructive impact on human destinies. It is defined that O. Bilash’s mono-opera has become a part of a general trend in the Ukrainian musical theatre of the 1960s–1970s associated with the tendency to chamberization and psychologization of opera. It has caused the exceptional popularity of the one-act monodrama genre among contemporary composers (V. Hubarenko, H. Zhukovskyi, Y. Ishchenko, etc.). It is described that I. Drach’s poetic text is used as the basis for the mono-opera with minor modifications (the changes have affected the title and only a few phrases). The structure of the poetic text has a significant impact on the composition of the mono-opera (the central episode is the protagonist’s story about the circumstances surrounding her birth, the extreme sections contain her beloved addresses). The connection between the opera’s system of leitmotifs and key phrases in the poetic text is detected. The leitmotifs are important in cementing the form of the mono-opera – it is in their repetition that the unifying role of the principle of through refrain is revealed. The Ballad of War contains two figurative and intonational spheres of war (scherzo, sharp dissonance, cluster consonances, chromatisation, grotesque syncopated rhythms, «cold» orchestral origin) and peace («warm» vocal origin, ariosity, melodic recitative, songfulness, vocalisations, luxurious Bilash’s melodies). O. Bilash has used various household genres actively: alullaby (an image of the incessantness of Life), a march («military» heroics), a cancan (personification of the image of aggression and spirituality), a Boston waltz (lyrical reflection and psychological solution). The composer uses the technique of stylizing church singing. The technique of sound imitation (movement of a steam locomotive, steam claps) is equally important. O. Bilash’s The Ballad of War mono-opera is a bright, original work and plays an important role in the development of the mono-opera genre both in the composer’s heritage and in Ukrainian music of the 1960s–1970s in general.