Watchdog American Oversight is suing for documents it believes could illustrate the full scope of white supremacist activity and ideology among troops.
The mistake meant about 7,400 soldiers sent to the Texas-Mexico border under Operation Lone Star were hit with higher-than-expected federal income taxes.
Under Texas law, officials can withhold police records if no one was convicted. In some cases, this has kept soldiers' suicide records from their families.
By Vianna Davila, The Texas Tribune and ProPublica