First Battle of Deneva

The First Battle of Deneva was a battle between the Romulan Star Empire and United Earth over Deneva.

Background
After the Vulcan refusal to fight against the Romulans in the war they installed warp detection grids in all of the Coalition's systems. However, the Romulans discovered a way to circumvent these systems, allowing them to surprise unsuspecting Starfleet ships. 

The Battle
The USS Yeager (NCC-76) was on patrol near Deneva when Romulan vessels entered the system and attacked the Yeager. The attack took Yeager entirely by surprise and led to it's destruction. Then, a short time later, the Tellarite warship Miracht entered the system and was engaged by the Romulans who attempted to take over the ship with their remote capture device. In order to stop the Romulans from capturing one of Tellar's strongest warships the ship's captain, Prev, fired a weapon into the ship's warpcore, destroying the entire ship. 

Aftermath
This was the first major loss for the United Earth, with a major colony world being lost. It also showed that their were problems with the warp detection grids installed by the Vulcans.