Prokofiev's compositional output during the years 1939-1944 was exceptional in both quantity and quality. The War Years spawned many of Prokofiev's greatest works, including the trilogy of the Sixth, Seventh and Eighth Piano Sonatas, known as the "War Sonatas." Focusing on the Seventh and Eighth Sonatas allows for a comparison of these, the most closely related of the three. Written almost simultaneously, the Seventh and Eighth Sonatas share an intricate unity although their contrasting elements are many. Prokofiev's versatility and genius in the use of motivic and cyclic elements links the movements of each sonata, and, ultimately, the two sonatas. Because of the motivic nature, which can be quite subtle, a Schoenbergian "Grundgestalt" method of analysis is used. Not solely a unifying device, the motives and their manipulation also create the drama of these highly charged works. Consequently, performance can be enlightened and enhanced through a detailed motivic study of both sonatas. Chapter One explores the historical context of the War Sonatas and an overview of Prokofiev's piano works, focusing on the nine Piano Sonatas. In Chapter Two, the structural relationships, motivic material, and stylistic differences of Sonata No. Seven and Sonata No. Eight are summarized. The introductory theme of the Seventh Sonata, its "Grundgestalt," contains all of the other themes in essence. Chapter Three examines how the drama of the sonatas influences their structure and the use of their motives. The Seventh Sonata is subjected to formal, tonal, and motivic analysis. Chapter Four continues the process with a full analysis of all three movements of Sonata No. Eight. In conclusion, these ideas are brought together in an overview of performance practice in the Seventh and Eighth Sonatas.