This collection consists of 17 letters Marinus Heyboer wrote to his brother Harry while training with the United States Army's 308th Field Artillery Regiment and 310th Field Hospital at Camp Dix, New Jersey, between February and April 1918. Heyboer discussed his training exercises, food, and other aspects of military life, in addition to responding to news of Harry's wife and young child.
Marinus composed 7 dated letters at Camp Dix between February 23, 1918, and late April 1918, as well as 10 undated letters covering the period between his arrival at Camp Dix and his departure for Europe. After initially joining Battery B of the 308th Field Artillery Regiment, Heyboer began medical training with the 310th Field Hospital. He told Harry about several training exercises, such as drilling, attending lectures, practicing with field guns, and experiencing gas in the "gas chambers." He also commented on his experiences with horses, which included cleaning up after the animals and witnessing a fatal accident. Heyboer frequently responded to news of his parents and inquired about Harry's wife and baby, Marie and Harry Jr. In one letter, he described two African American regiments that were also training at Camp Dix (March 16, 1918).