In October 3058, the leaders of the Successor States, along with the heads of two of the largest Periphery nations, met on the Lyran capital Tharkad, with the aim of accomplishing something that four Succession Wars had failed to achieve - the reformation of the Star League. Although the centuries-old divisions and mistrust were as strong as ever, they had one common cause in which they were united...to drive the Clans from the Inner Sphere.

Realising it would be futile to attempt to take on all the Clans at once, it was decided to target a single Clan and utterly destroy it, to prove to the others that the Inner Sphere was a force to be reckoned with. The Smoke Jaguars were selected, since they had been the most vicious and ruthless of the invading Clans, therefore incurring the greatest wrath and invoking the greatest desire for vengeance among the Successor States. To begin with, the aim was merely to drive them out of their Occupation Zone. However, information obtained from a Jaguar defector, fleeing charges of dishonourable conduct, gave them sufficient information about the Exodus Road, (the route taken 300 years earlier, by Alexander Kerensky and the SLDF when they left the Inner Sphere), to allow them to plan a mission to strike at the Jaguar homeworld of Huntress.

Operation Bulldog, the mission to drive the Jaguars from the Inner Sphere, was initiated in 3059 and lasted well into 3060. It began with a series of raids to disrupt communications and destroy supply depots, before efforts to decimate the Jaguar forces began in earnest. It was a total success and the handful of surviving Jaguars, gathered what ships they could muster and fled back to Huntress...for all the good it did them. Meanwhile the second mission, codenamed Task Force Serpent, followed the Exodus Road, back to the Jaguars' homeworld and launched an all-out invasion, bent on destroying troops, equipment, industrial facilities and the greatly-prized genetic repository. Despite the Jaguars mounting a suicidal last-ditch stand, they could not prevent the annihilation of their Clan as a viable fighting force.

Once the Jaguars had been dealt with, Victor Steiner-Davion set about ending the threat of invasion from the other Clans. Leading Task Force Serpent to Strana Mechty - homeworld of all the Clans, as well as their seat of government - he challenged each of the Crusader Clans (those who sought to conquer the Inner Sphere) to send forces to fight the various units of the task force, in a Trial of Refusal, fought in various locations across Strana Mechty. Ultimately, the combined forces of the new Star League emerged victorious. Having been defeated by the Inner Sphere, on their own soil and on their own terms, the Clans had little choice but to accept the terms laid out by Prince Victor. For the foreseeable future, they would not be making any further inroads into the Inner Sphere.

In contrast, two of the Warden Clans who had been involved in the invasion, sought to create closer ties with the Inner Sphere though peaceful means. Clan Nova Cat, for their assistance in the destruction of the Smoke Jaguars, were granted a number of worlds on which they could build permanent colonies. This later became known as the Nova Cat Prefecture. In return, the Nova Cats formally attached their touman, or military forces, to the Star League Defence Force. This was considered an act of treason by the Crusader Clans, who successfully petitioned for the Nova Cats to be Abjured, or cut off from the rest of the Clans and their holdings in the homeworlds to be forfeit. Clan Ghost Bear had already been conducting low-key operations to tranfer its people from the homeworlds to their Occupation Zone, for some time. By the time Task Force Serpent won its victory on Strana Mechty, the transition was complete. Their territory, formerly part of the Free Rasalhague Republic, became known as the Ghost Bear Dominion.

Further infighting among the Clans saw the Steel Vipers challenge the Jade Falcons, for outright control of their shared Occupation Zone, only to be soundly beaten, to the extent they were forced to withdraw completely and head back to the homeworlds in humiliation.

The first signs of trouble for the new Star League surfaced when Prince Victor returned home in late 3061. Having appointed his youngest sister Yvonne as Regent of the Federated Suns, before his departure, he came back to find her deposed and his other sister Katherine in control of a reunited Federated Commonwealth. By this time, she had renamed herself Katrina, after her grandmother and had dropped the Davion from her surname. Nothing, if not ambitious, Katrina also had her eye on the mantle of First Lord of the Star League. Meanwhile, Anastasius Focht, named Victor as his successor. The Prince's new role as Precentor Martial, however, did nothing to diminish his influence with the other heads of state and he was able to ensure his own preferred candidate, Co-ordinator Theodore Kurita of the Draconis Combine, was elected instead.

The first serious strain was put on the alliance when the Capellan Confederation launched a war of conquest aginst the St Ives Compact, successfully re-absorbing its worlds after two years of bitter fighting. In the process, it also reclaimed several other former Capellan worlds in the Chaos March.

It came close to total implosion when two years of growing unrest within the Federated Commonwealth, erupted into all-out civil war in 3063, as citizens and military units still loyal to the Davion side of the ruling family, fought to free themselves from Katrina's rule. Despite being officially employed by Comstar, Victor, along with close friends and former subordinates, played a major role in guiding the Davion loyalists to victory, although it came at the cost of 4 years of bitter fighting. Few worlds were left unscarred by the war, as formerly allied units, friends, neighbours and even families were forced to decide where their ultimate loyalties lay. The loss of life and devastation were on a scale unseen since the Fourth Succession War.