Third Succession War
The Third Succession War began in 2866. It is generally agreed that the war ended in 3025, but fighting continued sporadically until 3028 when the Fourth Succession War was officially started by the Federated Suns' attack on the Capellan Confederation following the marriage of Hanse Davion and Melissa Steiner. The years between the end of the conflict and the start of the Fourth Succession War were marked with almost constant, but low-intensity, warfare.
The Third Succession War began when Draconis Combine forces attacked Lyran Commonwealth coreward holdings. The intensity of this conflict never approached that of either the First or Second Succession Wars. This lessening was more likely due to reduced military capacity rather than a change of tactics. The scavenger necessities from the Second war carried over and each house rapidly realized that they needed to preserve their precious technical resources.
Two main components of this era were the evolution of a set of informal rules of engagement, similar to old Terran chivalric values, and a feudal system. The rules of engagement were similar to the Ares Conventions whereby 'Mech forces fought over industrial facilities, but were restricted in their attacks on those facilities and civilians. Especially important was a tradition of paying a ransom for safe passage after surrendering to a superior force. Also, JumpShips became strictly off-limits as a military target as it was quickly recognized that without JumpShips, nothing would be possible.
The feudal system evolved throughout the years because the capacity for central governance had evaporated. As a result, each Successor Lord controlled their house via a hierarchy of nobles who, in exchange for full authority of their worlds, pledged their fealty and their 'Mechs to their liege lord.
 Notable events of the Third Succession War
 The Great Lee Turkey Shoot
- See the Great Lee Turkey Shoot page for more detailed information.
Choosing to combat the increasing weakness of the Capellan ground forces in the late 30th Century with overwhelming air support, after a House Marik raid near Ingersoll in 2952 was repulsed without a single Liao loss, Chancellor Ingrid Liao decided to launch a major offensive against the Davion-held world of Lee. Site of a AFFS regional supply center as well as a critical maintenance facility for AeroSpace Fighters and increasingly rare Land-Air 'Mechs, Ingrid committed six fighter regiments (over 200 AeroSpace Fighters) and a sizable ground force to the mission.     
The MIIO however learned of the plan well in advance, giving First Prince Peter Davion plenty of time to reinforce and direct the planet's defense himself. Thanks to their advanced warning the Davion defenders met the Capellan forces in space, immediately assuming aerospace superiority. The Battle of Lee, later more commonly called the Great Lee Turkey Shoot, saw the sleeker and faster Davion AeroSpace Fighters easily cripple over over forty of the slower and older Capellan Thunderbird and Eagles, the Liao 'Mechs, tanks and infantry lacking sufficient air-cover and taking heavy losses before being pushed off-world.      
 The Deep Raid of 2987
- See the Deep Raid of 2987 page for more detailed information.
Shortly after becoming Archon, Alessandro Steiner reviewed intelligence reports with his Strategies and Tactics division and came to the realization that a lull in the fighting between Houses Marik and Liao presented a unique opportunity. With both sides having pulled back to regroup and recoup their losses after years of heavy fighting, Alessandro correctly guessed the Marik troops on the border would be relaxed and vulnerable to an attack from an unexpected quarter, including those guarding a "secret" BattleMech factory under construction on the League world of Ling.     
Sending the elite 6th Lyran Guards and the 54th Fighter Support Wing aboard a JumpShip diguised as a commerical freighter, after two months of tense jumps, the Steiner forces reached the Ling system unchallenged, destroying the BattleMech factory with only minimal losses to themselves. While the the League forces extracted a measure of revenge by inflicting heavy losses when the Lyran forces made ill-considered strikes against Park Place, Ryerson, Irian, Nathan and Bordon as they made their way back to Commonwealth space, the loss of vital BattleMech factory was a bitter blow.   
Recognizing humanity's slow but steady slide away from the glories of the Star League era and toward barbarism, Archon Katrina Steiner of the Lyran Commonwealth issued a Peace Proposal to the other House leaders in 3020. Hanse Davion, Prince of the Federated Suns, was the only Successor Lord who welcomed the initiative. Announcing that he would "take history by the throat," Davion began negotiations with the Archon. The result of these talks was the Federated Commonwealth Alliance Document, which Prince Hanse Davion and Archon Katrina Steiner signed on Terra in 3022. In addition to trade and military agreements, the F-C Document contained a secret provision betrothing the Archon's daughter in marriage to Hanse Davion. Though the marriage would not occur until the twelve-year-old Melissa came of age, this was the first step on the road to eventual unification of the Lyran Commonwealth and the Federated Suns.
The other three Successor Lords were aghast at this sudden shift of power, which would lead to the eventual creation of a single state nearly as large as their three Houses combined. In October 3022, the Draconis Combine, the Free Worlds League, and the Capellan Confederation hastily signed the Concord of Kapteyn. The scope of the Concord was not as far-reaching as the F-C Document, however. It called mainly for an end to active hostilities between the three states, who now pledged mutual defense instead. This new relationship would also permit the three parties to coordinate their overt and covert efforts at derailing the Davion-Steiner alliance.
Perhaps most active in the covert attempts was the Capellan Confederation under the leadership of Chancellor Maximilian Liao. Liao agents had already subverted Hanse Davion's brother-in-law Michael Hasek-Davion, who was now providing them with valuable military intelligence. When the Chancellor next initiated a scheme to kidnap and kill Hanse Davion in order to replace him with a clone his scientists had created, he went too far. Davion eventually escaped capture and imprisonment and returned to his place on the throne, vowing revenge.
- ↑ 1.0 1.1 House Liao (The Capellan Confederation), p. 50 "History - The Succession Wars - Shift to Aerospace"
- ↑ 2.0 2.1 House Davion (The Federated Suns), pp. 87-88 "History - Third Succession War - Knights of the Void"
- ↑ 3.0 3.1 Handbook: House Davion, p. 67 "History of the Federated Suns - Third Succession War - Rise of Brotherhoods - The Purge"
- ↑ 4.0 4.1 Handbook: House Liao, p. 34 "History of the Nation - Third Succession War - The Great Lee Turkey Shoot"
- ↑ 5.0 5.1 Technical Readout: 3025, p. 134 "AeroSpace Fighters - SPR-H5 Sparrowhawk"
- ↑ 6.0 6.1 Technical Readout: 3025 Revised, p. 152 "AeroSpace Fighters - SPR-H5 Sparrowhawk"
- ↑ 7.0 7.1 7.2 House Steiner (The Lyran Commonwealth), p. 77 "Alessandro Steiner"
- ↑ 8.0 8.1 House Marik (The Free Worlds League), pp. 46-47 "Concession to Parliament"
- ↑ 9.0 9.1 Handbook: House Steiner, p. 51 "Strategic Errors"
- ↑ 10.0 10.1 Technical Readout: 3025, p. 162
- Start Date - 2866
- End Date - 3025