The Tandarans were a humanoid race that originated on Tandar Prime.
The Tandarans were at war with the Suliban Cabal since 2144. Shortly after the war began, the Tandarans began questioning the loyalty of the unallied Suliban living in the Tandar sector. They were relocated to places such as Detention Complex 26 "temporarily." Years later, they were still waiting to be released. (ENT: "Detained")
In February 2152, Jonathan Archer encountered a physically altered Tandaran agent named Keyla on Risa. (ENT: "Two Days and Two Nights")
The rank pips of the Tandarans may be a reuse of the rank pips used by the crew on the USS Relativity from VOY: "Relativity". The same pins were also re-used for the Lokirrim in VOY: "Body and Soul".
A Tandaran security patch, a seven-pointed star, was among the items which were sold off on the It's A Wrap! sale and auction on eBay.