A Cardassian planet where the Eleventh Order, half a million strong, was wiped out by Klingon forces in 2375 after the Dominion declined to reinforce it.
Septimus III is a Cardassian-held world mentioned in the Deep Space Nine episode Strange Bedfellows (2375).
The Klingons move to invade the planet, which is defended by the Cardassian Eleventh Order, a force of some five hundred thousand troops. Damar asks Weyoun for reinforcements and is assured that the matter is in hand. No help is sent, and the whole garrison is destroyed. Weyoun treats the loss as an acceptable price.
The episode shows the death of the Eleventh Order as the final insult for Damar, already angered by the concessions made to the Breen. He stops drinking, frees Worf and Ezri Dax from execution and begins his revolt.