The one and the only battalion which has been in the United States Army Reserve is the 100th Infantry Battalion. During the World War II (WWII) the Nisei battalion was considered as the primary unit and comprised of members mainly from the Hawaii Army National Guard. The 100th infantry battalion also played a part in the WWII by joining with the 442nd Infantry Regiment which was also another Nisei military unit and thereby became a single and heavy combat team. Having based in Honolulu, Hawaii, the battalion got it reserves from Hawaii, Guam, American Samoa and Saipan. The 100th infantry battalion was so popular that it had earned a nickname known as “Purple Heart Battalion” which meant ‘Remember Pearl Harbor.’

The formation of the 100th Infantry Battalion is an interesting series in history. When the Battle of Midway was in progress, the Nisei unit belonging to the Hawaii National Guard took all its weapons and soldiers and started sail to the port of Oakland where it formed the 100th Infantry Battalion in 1942. The reason why the 100th Infantry battalion got suddenly created comprising of 1432 Nisei especially in the midst of Battle of Midway was to help the Japanese Americans who were serving in the U.S. army to prove their patriotism to the United States of America. The country has already seen the chaos following the Pearl Harbor attack in December 1941 which caused the Japanese Americans or soldiers of Japanese ancestry seen as enemy aliens. About 2000 Japanese American soldiers wanted to serve the United States of America and show their loyalty to the country. Hence the 100th Infantry Battalion was formed, unlike the pre-war army procedures. The 100th Infantry Battalion came under a new system of organization where it did not require the battalion to be a part of a regiment and therefore did not attach itself to a regiment. The 100th Infantry Battalion earned an unofficial name called the One-puka-puka.

One of the toughest challenge faced by the Nisei soldiers of the 100th Infantry Battalion was distrust and hostility by the fellow soldiers, the military units and the political leaders of the United States. The Nisei soldiers had to undergo severe training such as physical, psychology, tactical and marksmanship at Camp McCoy, Wisconsin before they got permanently placed in the military units. They even got employed in the rescue of local civilians who were drowning in the frozen lake eat Wisconsin to prove their faithfulness and bravery. Five soldiers among them received the Soldier’s Medals. After about six months of training at Camp McCoy, the 100th Infantry Battalion got sent to Camp Shelby in Mississippi where it got attached to the 85th Division. Here the Nisei soldiers received a more tough training along with skepticism. Following Camp Shelby, the Nisei soldiers got moved to Louisiana at Camp Clairborne where there got employed in war games and field exercises. Finally, the 100th Infantry Battalion passed their all their intense and advanced forms of training successfully and joined the 442nd Regiment Combat Team in 1943.