The 442nd Regimental Combat Team/100th Battalion was the most decorated for its size and length of service unit in U.S. Military history. The caveat is put there to avoid comparing apples and oranges.

An interesting thing here is that the most decorated American unit was Japanese. That's why many people in the country don't know about it. The 442nd Regiment consisted of soldiers of Japanese ancestry, and most of the officers were Caucasian. All the soldiers were born in the USA, most of them didn't even speak Japanese. During WWII they fought in Europe, showing incredible courage, power and endurance.

The original 4,000 Nisei who initially came in April 1943 had to be replaced nearly 3.5 times. In total, about 14,000 men served, ultimately earning Seven Presidential unit citations, 15 battlefield commissions, 9,486 Purple Hearts (many earning double and triples), 4,000 Bronze Stars. 1,200 Oak Leaf Clusters added to the Bronze Star, 560 Silver Stars, 28 Oak Leaf Clusters to the Silver Star, 52 Distinguished Service Crosses, and 23 of America’s highest decoration, the Medal of Honor. Eventually, 14,000 soldiers would serve in the regiment, with more than 700 members killed or missing in action.

More Info: zidbits.com