Union forces in the Civil War needed far more Engineers than the Regular Army could furnish. Volunteer Engineers, who entered the Army for wartime service only, supported operations just as did the regulars. Their contributions ranged from constructing pontoon bridges under fire to building field fortifications for siege operations. Thomas Owen's letters and diary reveal the life and duties of a volunteer Engineer who served as a sergeant and company-grade officer. These writings convey his reactions to the extreme conditions of wartime, from the rigors of combat to the boredom of camp life. For their insights into the thoughts and feelings of an Engineer at war and descriptions of Civil War combat engineering, they should still interest those of us who serve as Army Engineers. Paul Taylor Colonel, Corps of Engineers Chief of Staff