Battalion History

Origins
The 100th Infantry Battalion was formed during a time of great turmoil and fear in the Territory of Hawaiʻi and across the United States. On December 7, 1941, Japan launched a devastating surprise attack across the island of Oahu, striking Pearl Harbor, home of the United States Pacific Fleet, as well as nearby military airfields and installations, in what became known as the Attack on Pearl Harbor. In the weeks that followed, there was widespread apprehension that Hawaiʻi might soon be invaded. Residents of Japanese ancestry in Hawaiʻi and on the mainland United States were increasingly viewed with suspicion and hostility by many Americans.

Formation of the Hawaiian Provisional Infantry Battalion
The predecessor to the 100th Infantry Battalion was the Hawaiian Provisional Infantry Battalion, established in May 1942 as a racially segregated unit composed primarily of Americans of Japanese ancestry (AJA). Many of these men had already been serving in the Hawaii National Guard, which was federalized into the United States Army after the Selective Training and Service Act of 1940 brought its 298th Infantry Regiment and 299th Infantry Regiment under Army command. These soldiers were already on duty defending the islands during the Attack on Pearl Harbor on December 7, 1941.

In January 1942, the United States War Department reclassified Japanese Americans as IV-C, the Selective Service System category used for “enemy aliens,” making them ineligible for military induction. However, Americans of Japanese ancestry already serving in uniform continued to carry out their orders to defend the Territory of Hawaiʻi.

Shortly before the Battle of Midway, the United States War Department, wary of the loyalty of Japanese Americans, removed these men from their multiethnic units to form the Hawaiian Provisional Infantry Battalion. On May 28, 1942, AJA soldiers from the 298th Infantry Regiment and 299th Infantry Regiment of the Hawaii National Guard, along with activated reservists, regular Army personnel, and soldiers from engineer units in Hawaiʻi, were assembled at Schofield Barracks and assigned to the newly formed unit.

100th Infantry Battalion (Separate) — Mainland Training

On June 5, 1942, the 1,432 officers and enlisted men of the newly formed Hawaiian Provisional Infantry Battalion quietly departed Honolulu in great secrecy aboard the USAT Maui. They represented a small group drawn from a population of roughly 280,000 people of Japanese ancestry living in the United States — about 160,000 in Hawaiʻi and approximately 120,000 on the U.S. mainland. Its members made up only about 0.5% of the Japanese-ancestry population at the time — many of whom were living under martial law in Hawaiʻi or incarcerated on the mainland. These soldiers carried a tremendous responsibility to demonstrate loyalty and help create a positive legacy for Japanese Americans and for other communities of color. With the exception of a few Caucasian officers and about 20 men of Hawaiian and other Asian ethnicities (including those who were of mixed ethnicities), it was the first segregated combat unit of American soldiers of Japanese ancestry (AJA) during World War II.

Arriving in Oakland, California on June 12, 1942, the Hawaiian Provisional Infantry Battalion was officially activated and designated the 100th Infantry Battalion (Separate). It was an “orphan battalion,” not assigned to a regiment or larger Army unit. The battalion gave itself the nickname “One Puka Puka” — the zeroes resembled a hole, and “puka” means “hole” in Hawaiian. The men of the 100th adopted “Remember Pearl Harbor” as their motto, reflecting their outrage at the attack on their homeland, Hawaiʻi, and their country, the United States.

The men were transferred to Camp McCoy, Wisconsin for training. While there, the men had the foresight to lay the foundation for a postwar club where the veterans could continue their camaraderie and provide mutual assistance and support to one another, including to the families of their comrades who gave their lives in the war. Subsequently, the soldiers began contributing $2 from their monthly pay to contribute to a fund for this organization, and a 100th Infantry Battalion Clubhouse.

The 100th would undergo extensive training in Wisconsin, Mississippi, and Louisiana from June 1942 until August 1943 while government and military officials observed the unit to decide how these soldiers would be used. The battalion’s outstanding performance and training record were key factors leading the United States War Department to resume allowing Americans of Japanese ancestry to volunteer for military service, resulting in the formation of the 442nd Regimental Combat Team (RCT) in February 1943.

Combat in Italy and France
Attached to the 133rd Infantry Regiment, 34th Infantry Division of the Fifth Army, the 100th Infantry Battalion (Separate) landed at Salerno, Italy on September 22, 1943, with just over 1,300 men. It headed into combat at Salerno in southern Italy on the night of September 26. It first engaged in active combat on September 29, when Sgt. Shigeo “Joe” Takata (Co. B) became the first from the 100th — and the first soldier in an AJA unit — to be killed in action. By the end of February 1944, after heavy fighting from Salerno to Cassino, the unit’s effective strength had dropped to approximately 460 men. The high number of casualties sustained during its first five months in combat earned the 100th Infantry Battalion the nickname, “The Purple Heart Battalion.”

The valor of the 100th Infantry Battalion in its first weeks in Italy convinced the War Department that American soldiers of Japanese descent could be trusted in combat, thus clearing the way for the 442nd RCT to join the 100th Infantry Battalion in Italy. In March 1944, the first group of men from the 442nd RCT arrived as replacements to replenish the 100th’s depleted ranks. After the regiment arrived in Italy in June 1944, the 100th was attached to the 442nd Infantry Regiment, serving as its 1st Battalion. On August 10, 1944, the 100th Infantry Battalion (Separate) was officially redesignated, “100th Battalion, 442nd Infantry.” Due to its outstanding record in training and combat, the battalion was allowed to keep its unit’s numeric “100th” designation. Together, the 100th and 442nd would become one of the most decorated units in U.S. military history.

Legacy and Honors

A number of factors contributed to the outstanding combat performance of the 100th Infantry Battalion and later the 442nd RCT. Although the men averaged about 5’4″ in height, typically weighed less than most mainland trainees, and had an average age of about 24 — considerably higher than that of most infantry troops — they were physically fit and well trained. Teamwork was strongly emphasized throughout their training. While the battalion had its share of “hell-raisers,” most soldiers were determined that the actions of a few would not damage the reputation of the entire unit. They were also motivated by a common goal – to prove their loyalty. The soldiers understood that their actions would influence how all AJA were viewed and felt a strong responsibility to set an example and bring honor to their communities as loyal Americans. The men of the 100th demonstrated remarkable personal discipline, perseverance, and sense of duty, with no known cases of soldiers going AWOL (Absent Without Leave). The 100th would, however, have cases of “reverse-AWOL,” where soldiers returned to the battalion for combat duty before their wounds were fully healed, foregoing reassignment or extended medical leave.

Despite its inauspicious beginnings, the 100th Infantry Battalion (Separate) became a legendary combat unit during its 20 months in Europe, serving from September 1943 to May 1945, when Germany surrendered. By that time, 3,147 men were recorded as having served in the 100th Infantry Battalion, and the number of lost lives would eventually total 340.

The 100th Infantry Battalion fought in six campaigns in Italy and France and earned three Presidential Unit Citations — the first earned by the 100th Infantry Battalion (Separate) for neutralizing a strongly defended German center of resistance at Belvedere. Within the 100th Infantry Battalion, one soldier, Pfc. Sadao Munemori, was posthumously awarded the Medal of Honor — the nation’s highest combat decoration for gallantry in action above and beyond the call of duty. Moreover, 24 members of the battalion earned Distinguished Service Crosses (7 of which were upgraded to Medals of Honor in 2000), 147 received Silver Stars and 238 were given Bronze Stars with a bronze “V” for valor. A total of 1,703 Purple Hearts were awarded to members of the 100th Infantry Battalion for those wounded or killed as a result of enemy action. For meritorious service, the Legion of Merit went to nine, and the Bronze Star to 2,173.

On November 2, 2011, the deeds of the 100th Infantry Battalion, the 442nd Regimental Combat Team, and the Military Intelligence Service (MIS) that had operated against Japanese forces in the Pacific were recognized again for exemplary service to America. Veterans from the three units gathered in Emancipation Hall in Washington, D.C., to receive a Congressional Gold Medal. Back in Hawaiʻi, they were joined by veterans of the 1399th Engineer Construction Battalion, who were recognized for their vital wartime service on Oʻahu. All were honored with a festive salute from their home state of Hawaiʻi, honoring their extraordinary service and sacrifice for the United States.