How did Russian folk music influence Claude Debussy’s use of scales?

Claude Debussy’s exploration of Russian folk music was a significant factor in his departure from traditional Western functional tonality. Specifically, he was influenced by the modal scales found in Russian folk music, which provided an alternative to the major and minor scales that had dominated Western music for centuries.1

By incorporating these modal influences, alongside other inspirations such as Indonesian music and Impressionist painting, Debussy moved toward a more fluid harmonic style. This shift led him to utilize devices like the whole-tone scale, which lacks the traditional distribution of whole and half steps that define major and minor keys. Because this scale does not allow for the standard harmonic resolutions found in common practice, it enabled Debussy to create music that existed without traditional tonal centers, as famously demonstrated in his piano prelude "Voiles".12