Question: Susumu Ito was assigned to which Japanese-American part of the US Army Reserve?

full_context: Document 1: Only the Brave (2006 film): Only the Brave is a 2006 independent film about the 100th Infantry Battalion/442nd Regimental Combat Team, a segregated World War II fighting unit primarily made up of "Nisei" Japanese Americans, which for its size and length of service became the most decorated unit in U.S. military history. The film, produced and directed by Lane Nishikawa is a fictionalized account of the rescue of the Lost Battalion.
Document 2: 204th Brigade Support Battalion (United States): The mission of the 204th Brigade Support Battalion, "Rough Riders," is to, on order, deploy and execute responsive Combat Service Support and Combat Health Support in support of the 2nd Brigade Combat Team, 4th Infantry Division's objectives. ("Rough Riders") was originally constituted as the 5th Sanitary Trains on 10 November 1917 at Camp Logan, Texas. During World War I, the unit fought in numerous battles and campaigns including the Battle of Saint-Mihiel, Meuse-Argonne Offensive, and the Battle of Champagne, at Lorraine. After the First World War, the unit was reorganized and re-designated on 29 January 1921 as the 5th Medical Regiment. The 5th Medical Regiment was inactivated in August 1921 at Camp Jackson, South Carolina.
Document 3: 506th Infantry Regiment (United States): The 506th Infantry Regiment, originally designated the 506th Parachute Infantry Regiment (506th PIR) during World War II, is an airborne light infantry regiment of the United States Army. Currently a parent regiment under the U.S. Army Regimental System, the regiment has two active battalions: the 1st Battalion, 506th Infantry Regiment (1-506th) is assigned to the 1st Brigade Combat Team, 101st Airborne Division, and the 2nd Battalion, 506th Infantry Regiment (2-506th) is assigned to the 3rd Brigade Combat Team, 101st Airborne Division.
Document 4: 332nd Engineer General Service Regiment: 332nd Engineer General Service Regiment or 332nd Engineer Regiment was activated as a Special Service Regiment in May 1942, as a unit in the United States Army. Later this unit was redesignated a General Service Regiment. The unit was formed from some regular Army officers and enlisted men, trained in the United States, then shipped overseas early in World War II to England. They were the vanguard of many others to follow, including infantry and armored troops. Their purpose was to build facilities in preparation for those to follow. After the Normandy Invasion, they followed the front lines constructing roads, railroad bridges, hospitals, and other infrastructure needed by the advancing Armies. Continuing through until surrender by Germany in 1945, the unit stayed on as part of the Army of Occupation. Many of the troops in the units were among those who were overseas for the longest periods of all in World War II.
Document 5: Lost Battalion (World War I): The Lost Battalion is the name given to nine companies of the United States 77th Division, roughly 554 men, isolated by German forces during World War I after an American attack in the Argonne Forest in October 1918. Roughly 197 were killed in action and approximately 150 missing or taken prisoner before 194 remaining men were rescued. They were led by Major Charles White Whittlesey. On 2 October, the division quickly advanced into the Argonne, under the belief that French forces were supporting the left flank and two American units including the 92nd Division were supporting the right flank. Unknown to Whittlesey's unit, the French advance had been stalled. Without this knowledge, the Americans had moved beyond the rest of the Allied line and found themselves completely cut off and surrounded by German forces. For the next six days, suffering heavy losses, the men of the division were forced to fight off several attacks by the Germans.
Document 6: 3rd Battalion, 187th Infantry Regiment: The 3rd Battalion, 187th Infantry Regiment, also known as the Iron Rakkasans, is a battalion of the US Army 187th Infantry Regiment. The battalion was activated on 25 February 1943, and first saw action in the Pacific Theater of the Second World War, during the battle to regain US control of the Philippines. Troops from the battalion then served in the four-year occupation of Japan, where they earned their nickname "Rakkasans" (meaning "falling down umbrellas"), before stationing in Fort Campbell, Kentucky. The battalion served in the Korean War from 1950 as the 187th Airborne Regimental Combat Team and participated in 12 major missions during the Vietnam War, emerging from that conflict as the US’s most highly decorated airborne battalion. In the 1990s the battalion served in Iraq as part of Operation Desert Shield and Operation Desert Storm, then in the first decade of the 21st century in Afghanistan and again in Iraq as part of Operation Iraqi Freedom. The battalion has received numerous awards and commendations, including six Presidential Unit Citations and four Valorous Unit Awards.
Document 7: 503rd Infantry Regiment (United States): The 503rd Infantry Regiment, formerly the 503rd Parachute Infantry Regiment (PIR) and the 503rd Airborne Infantry Regiment (AIR), is an airborne infantry regiment of the United States Army. The regiment served as an independent regiment in the Pacific War during World War II; at Fort Campbell, Kentucky; in Okinawa, Japan; and in Germany. Regimental elements have been assigned to the 2nd Infantry Division, the 11th Airborne Division, the 24th Infantry Division, the 82nd Airborne Division, and the 173rd Airborne Brigade Combat Team. Regimental elements have participated in campaigns in the Vietnam War, Operation Enduring Freedom–Afghanistan, and Operation Iraqi Freedom. The regiment claims 15 Medal of Honor recipients: two from World War II, 10 from Vietnam, and three from Afghanistan. A parent regiment under the U.S. Army Regimental System. The regiment's 1st and 2nd Battalions are active, assigned to the 173rd Airborne Brigade, based at Caserma Ederle, Vicenza, Italy.
Document 8: Susumu Ito: He was in auto mechanic school when he was drafted into the military in 1940, two years before the Japanese attack on Pearl Harbor. He worked as a mechanic, but was eventually assigned to the all Japanese-American 442nd Regimental Combat Team, which became the most decorated unit for its size and length of service in the U.S. Army during World War II. He was an artillery spotter (forward field observer) assigned to C Battery. He was promoted to the rank of second lieutenant on October 19, 1944. Ito participated in the famous rescue of the "Lost Battalion", the first battalion of the 141st U.S. Infantry Regiment of the 36th Texas Division. The action took place in the Vosges Mountains, in France, in October 1944. Both units were attached to the Seventh U.S. Army. The Lost Battalion had been cut off and surrounded by the Germans. Lt. Ito was attached to I Company of the 442, which effected the rescue of the Lost Battalion. Though the 442nd suffered extremely heavy casualties in the engagement, Ito emerged unscathed. He was attached to I Company, of which only eight members survived this action. Of the rescue, Ito later recalled, "Looking back, it wasn't an easy outing, but having come through it intact, it was an experience that cannot be forgotten or easily duplicated. At the time, I thought that this was more or less a typical battle encounter with a strong enemy and not a special or unique mission. I guess my analysis is not shared by history." The U.S. Army later declared the Rescue of the Lost Battalion to be one of the top ten battles of the U.S. Army in its history.
Document 9: Crystal City Internment Camp: Crystal City Internment Camp, located near Crystal City, Texas, was a place of confinement for people of Japanese, German, and Italian descent during World War II and has been variously described as a detention facility or a concentration camp. The camp, which was originally designed to hold 3,500 people, opened in December 1943 and was officially closed on February 11, 1948. Officially known as the Crystal City Alien Enemy Detention Facility (more commonly referred to as U.S. Family Internment Camp, Crystal City, Texas), the camp was operated by the Immigration and Naturalization Service under the Department of Justice and was originally designed to hold Japanese families, but later held German families as well, including many who were deported from Latin American countries to the U.S. A significant number of those incarcerated were native-born American citizens. The Crystal City Internment Camp was one of the primary confinement facilities in the United States for families during World War II.
Document 10: Asian American women in World War II: Asian American women during World War II served many crucial functions that tend to be overlooked, or erased entirely, from modern history books. Women’s roles are under-appreciated or unmentioned in the context of war; these women, however, were tasked with various duties that greatly aided American forces going into combat. Japanese American women, known as “Nisei”, contributed to war efforts by providing medical care as nurses and doctors, as well as serving as military intelligence officials and linguists. These women were also on the front lines of combat in many instances, with Filipino American women fighting as an underground coalition resistance in the Philippines. Asian American women initially began their involvement with the formation of the Army Nurse Corps (ANC) and Women's Army Corps (WAC), serving as linguists and translators at Fort Snelling, Minnesota. Their roles became increasingly more prominent and involved, however, with the bombing at Pearl Harbor and the United States' entry into the war against Japan.
Document 11: Camp Douglas (Wyoming): Camp Douglas was an internment camp for Prisoners of War (POW) during World War II, located in the city of Douglas, Wyoming, United States. Between January 1943 and February 1946 in the camp housing first Italian and then German prisoners of war in the United States. While there are few remaining structures, the walls of the Officer's Club were painted with murals by three Italian prisoners. These paintings depicting western life and folklore are now registered with the United States Department of the Interior National Park Service on the National Register of Historic Places. The story of this POW camp is an important part of the history of the town of Douglas.
Document 12: 442nd Infantry Regiment (United States): The 442nd Regimental Combat Team is an infantry regiment of the United States Army, part of the Army Reserve. The regiment was a fighting unit composed almost entirely of American soldiers of Japanese ancestry (mostly from Hawaii) who fought in World War II. Most of the families of mainland Japanese Americans were confined to internment camps in the United States interior. Beginning in 1944, the regiment fought primarily in Europe during World War II, in particular Italy, southern France, and Germany.
Document 13: 100th Infantry Battalion (United States): The 100th Infantry Battalion is the only infantry unit in the United States Army Reserve. In World War II, the then-primarily Nisei battalion was composed largely of former members of the Hawaii Army National Guard. The 100th saw heavy combat during World War II before and after combining with the 442nd Infantry Regiment, another mostly Nisei military unit, into a single fighting combat team. Based at Fort Shafter, Honolulu, Hawaii, the 100th Battalion has reservists from Hawaii, American Samoa, Guam and Saipan, and has deployed to Iraq and Kuwait. The unit was unofficially nicknamed the "Purple Heart Battalion", with the motto "Remember Pearl Harbor".
Document 14: Lyle Bouck: Lyle Joseph Bouck, Jr. (December 17, 1923 – December 2, 2016) enlisted in the U.S. National Guard at age 14. During World War II, he was a 20-year-old lieutenant in charge of the Intelligence and Reconnaissance Platoon, 394th Infantry Regiment, 99th Infantry Division. On the first morning of the Germans' advance during the Battle of the Bulge, his 18-man unit along with four forward artillery observers held off an entire German battalion of more than 500 men for nearly an entire day, killing or wounding 92, and significantly delayed the German advance in a vital sector of the northern front. Every single member of the platoon was later decorated, making it one of the most decorated platoons in all of World War II. Bouck was one of the youngest commissioned officers in the U.S. Army.
Document 15: Japanese Americans: Japanese Americans (日系アメリカ人 , Nikkei Amerikajin ) are Americans who are fully or partially of Japanese descent, especially those who identify with that ancestry, along with their cultural characteristics. Japanese Americans were among the three largest Asian American ethnic communities during the 20th century, but since the 2000 census, they have declined in number to constitute the sixth largest Asian American group at around 1.3 million, including those of partial ancestry. According to the 2010 census, the largest Japanese American communities were found in California with 272,528, Hawaii with 185,502, New York with 37,780, Washington with 35,008, Illinois with 17,542, and Ohio with 16,995. Southern California has the largest Japanese American population in North America, and the city of Torrance holds the densest Japanese American population in the 48 contiguous states.
ground_truth: 442nd Regimental Combat Team