How were ethnic minorities discriminated against in the us military?

You didn't give a context, but let's look at ethnic minorities in the US military during World War II, and we'll just look at the case of African Americans.  Over 1 million African Americans were inducted into the armed forces during World War II.  But they were not treated as equals in the military.  Typically they were banned from front-line fighting and given lower tasks to perform.  (There were some exceptions to this, such as the invasion of Normandy and the Battle of the Bulge.)  They were frequently less well equipped and provided with gear and provisions.  They also did not receive military awards for their service in the way that white servicemen did.  (Some were finally recognized for their service decades later.)