The artist's initials are documented in a Soviet-era publication as "I.T." however a visual inspection of the poster indicates the initials are likely "B.T." While not verified, the artist might be Timofei Boichuk. See Boichuk, Timofei.
Sources & Citations
Soviet Posters of the era of the Civil War 1918-1921 by B. S. Butnik-Siverskii (1960), page 161, poster 229 (initials documented as I.T.)