Henry Marshall is among those writers whose letters provide insight into the workings of the mind, but also the workings of the heart. As a result, his surviving correspondence ranks among the outstanding collections in the Schoff Civil War Collections, providing a sensitive and deeply introspective view into the experience of a white officer in a "colored" regiment. An exquisite writer, Marshall was also among the most punctual of correspondents, rarely allowing a week to pass without sending something to his family at home. As a result of this fidelity and his meticulous eye for detail, it is possible to reconstruct nearly every day of Marshall's life under arms, the swings in his emotions, and the sudden changes in fortune that marked his career.
The high point of the collection is a remarkable series of letters written while Marshall was captain of Co. E, 29th Connecticut Infantry (Colored). Unlike the vast majority of white Americans, Marshall saw African-Americans as capable soldiers, brave and willing, and though afflicted with an unrelenting paternalism and sense of his own racial superiority, he generally refrained from swinging to the romantic extremes of many white abolitionists or the vicious extremes of his more racist compatriots. Marshall provides good accounts of daily life in camp, the inevitable rumors circulating among the soldiers, and opinions of officers. Of particular value are the ruminations on African American troops and their officers, living conditions while on duty guarding plantations in South Carolina or in the trenches before Petersburg, and the heavy labor while working at construction of the Dutch Gap Canal.
Among the military engagements described by Marshall are Fredericksburg, the sieges of Suffolk and Petersburg (particularly the battles of New Market, Darbytown Road and the Darbytown and New Market Roads), and the capture of Richmond. Furthermore, Marshall was involved in a number of minor skirmishes, many of which are exceptionally well documented. Overall, the best accounts are those for New Market Heights, where African American troops again distinguished themselves, and for a smaller, but significant skirmish during the Petersburg Campaign on October 12 and 13, 1864.
Marshall's letters are made more valuable in that his observational scope extends beyond the military, to report on such things as contraband children's schools (April 30, 1863), "shouts" and religious services (1864 July 5), and the local civilianry. An educated man with a keen interest in botany, he frequently sent home lengthy descriptions of southern flowers, often enclosing samples and seeds, and he left a rare record of the reading material available to a soldier. Marshall was also a keen observer of the religious life in his regiment, writing scathing attacks on his regiment's chaplain, whom Marshall felt was suspect of character.