A devout Seventh-day Adventist, Tatsuguchi studied medicine and was licensed as a physician in the United States (US). He returned to his native Japan to practice medicine at the Tokyo Adventist Sanitarium, where he received further medical training. In 1941, he was ordered to cease his medical practice and conscripted into the IJA as an acting medical officer, although he was given an enlisted rather than officer rank because of his American connections. In late 1942, Tatsuguchi was sent to Attu, which had been occupied by Japanese forces in June 1942. On May 11, 1943, The United States Army landed on the island, intending to retake American soil from the Japanese.