This book describes all Polikarpov’s original projects, both those put into reality and unimplemented ones. It took the author many years to prepare for the creation of the book. The author studied materials on the respective topics in all Russian archives, and made use of the recollections of Polikarpov’s contemporaries, as well as publications by other researchers. For purposes of clarity and in order to facilitate publication, the author split the book on Nikolai Polikarpov’s aircraft into two parts – the ‘Biplane Era’ and the ‘Monoplane Era’. Indeed, during the designer’s activity from 1918 through to 1932, he devoted himself predominantly to creating biplanes. For the 1920s, the biplanes were a preferable option; they were more common, more reliable, better studied, and even more desirable for the Red Army Air Force. The first design of the IL-400 (I-1) monoplane fighter appeared as early as 1923; however, it was through its novelty and unpredictability that the aircraft failed to achieve the deserved success. It should be noted that the U-2 (Po-2) and the R-5 biplanes, which were created during that period, became one of the best Polikarpov aircraft, and brought him recognition as a designer. In the 1930s, Nikolai Polikarpov’s activity reached its pinnacle. It was during that period that he created his advanced monoplanes such as the I-16, the I-17, the VIT-2, and others. He continued his fruitful and quite successful activity in the area of creating modern aircraft during the war of 1941—45 as well. Volume 2 comprehensively covers Polikarpov’s monoplane designs.