Exarch Levin after proclaimed the Republic Senate abolished after it was discovered that they were trying to usurp the government by controling various people in military and including the knights. Their plan was discovered by Paladin Victor Steiner-Davion and later assassinated for it.
Intially the group was referred to as Loyalist, the Loyalist held various parts of Terra, including some parts of Europe including entire nation-state of Germany, some part of North America, & South America. As rebellion spread, so did worlds to Senator's cause.
Early attempts were made to capture members of the Inner Sphere's leaders as they arrived, had failed.
Their military campaign was lead by former Knight and later Senator Conner Rhys-Monroe. He had masterminded military campaigns on Terra.
The Senate Alliance forces attempting to capture Paris, France and Leaders of the Inner Sphere who had gather for Steiner-Davion's funeral in June, 3135 as last attempt to regain control of the situation and end the "Civil War".
After being forced off Terra, the various senators returned to their worlds and prepared to fight the Republic. Conner Rhys-Monroe conceived the plan to take certain key worlds and formarlly create the Senatorial Alliance. He lead campaign from Markab to secure various worlds on his end to link the planets to worlds in Prefecture IV. He led a key battle on the world of Ronel for its functional HPG Station. He was defeated again by a Republic Coalition led by Julian Davion. Conner and his Senate forces surrendered and withdrew from Ronel back to Markab. At the same time, Liberty, the bridging world that linked Markab's side of Republic to Prefecture IV's worlds, was taken by Countess Tara Campbell. This effectively severed the alliance in half.
 Fortress Republic Era
To strengthen the Alliance military, a plan was hatch to take independant world of Irian and its 'Mech factories for the Alliance. In July, 3136, a company of BattleMechs were shipped secretly into the warehouse of the massive factory's Drop Port. When activated by an inside spy, the Senate Alliance forces attempted to take control of the facilities to secure the production runs. However, Irian planetary officials hired the newly formed mercenary battalion, the Wolf Hunters, who then attacked the raiders and destroyed them before they could take any of the cargo of newly built BattleMechs.
The Alliance has multiple names: Loyalists, Alliance of Senators, & Senate Alliance. The Senatorial Alliance name was being used by outside powers as of the novel To Ride the Chimera in game year 3138.
- ↑ Pandora's Gambit, p. 104, "Eagle Talon's take Park Place"