The SSV Tehran was an Alliance cruiser built on Mars that saw action in the First Contact War, where she helped evacuate the prototype Mark 38 Explosive Ordance Disposal Powered Ballistics Armor during Operation: Trail Blazer to Weaping Meadow University and provided low-orbit cannon support to assist the university, ending the siege.
Named for the Iranian capital, she was made in 2147 CE, and before her destruction in 2173 CE, she was the oldest ship still in operation in the entire Alliance fleet. The Tehran was mainly a 'for show' ship as her outdated effectiveness made her a liability in fleet combat. Her one deployment was in a battle against a group of turian pirates, where she suffered heavy damage.
After the battle the Tehran was assigned to protect the Sol System until 2173, when she was assigned to help escort a captured Batarian Hegemony VI containing proof that the batarians were hiring slavers and other criminals to raid human ships and colonies, which would give humanity a good reason to declare all-out war on the Hegemony. However, while traveling at light speed using a mass relay, unknown technology managed to pull the cruiser out of light speed and over the barren planet of Sadafeel, where she was ambushed by three large vessels of an unkown force or signature. An Alliance battle group managed to intervene, but not before the Tehran was put on a crash course for the planet.
A rushed rescue operation led by Maj. Adam Locke of the 92nd Shock Trooper Regiment managed to save some crew but many more lives were lost. The Tehran was left on the barren surface of Sadafeel, where she became a nest for the large birds of prey that populated the planet. Seven years later the Office of Alliance Territorial Hegemony sent a team led by Staff Sergeant Dylan Low to find the missing core, but the team found no results and a battle with large birds resulted in the deaths of everyone except Low. Following this failure, the ship was destroyed by a hydrogen bomb dropped from orbit by the Alliance to ensure no sensitive data could ever be salvaged.