The imprisonment by the Tandarans of Suliban civilians who had no connection with the Cabal, discovered when Jonathan Archer and Travis Mayweather were themselves held at Detention Complex 26.
In the Enterprise episode Detained, Archer and Mayweather stray into Tandaran military space in a shuttlepod and wake up in a prison camp full of Suliban. They assume the inmates are Cabal soldiers, but learn from a prisoner named Danik, held with his young daughter Narra, that these are ordinary citizens.
The Tandarans are at war with the Cabal and have interned every Suliban living in their territory, supposedly for their own protection. The camp's commander, Colonel Grat, is courteous to Archer but wants what Starfleet knows about the Cabal.
Archer refuses to leave quietly. With Enterprise drawing off the guards and Malcolm Reed slipping into the camp in disguise, he helps the prisoners reach their impounded ships and escape, knowing they still have a long way to travel before they are safe.