Considered a "dangerous enemy alien," Matahichi Iseri was separated from his family and sent to the Department of Justice internment camp at Fort Missoula, Montana. In June 1942, he received a Change of Residence Notice certificate, which indicated that his request to join his family at the Pinedale Assembly Center in California had been approved.

While he was at Fort Missoula, Montana, a Department of Justice internment camp for enemy aliens, Matahichi Iseri wrote to his wife and children, who were still awaiting a relocation assignment from the WRA.