...Inner Sphere Map courtesy of Solaris 7...

As copied/quoted from:  MechWarrior 4: Vengeance©™

"In the 31st Century, the fate of entire worlds hinge on the MechWarrior…

BattleMech 

BattleMechs, thirty-foot-tall engines of destruction.  Weighing up to a hundred tons and bristling with an awesome array of powerful weaponry, these fearsome war machines are piloted only by the best of the best, elite soldiers sworn to defend their Houses and homelands.  From the Capellan Confederation to the Free Worlds League, from the forces of House Davion to the intrigues of the Draconis Combine, the fate of entire worlds rests on the skill and daring of the MechWarrior!

World of MechWarrior 

It is the 31st Century, and mankind has spread across the stars.  The discovery of feasible faster-than-light travel in the year 2108 was humanity's first step toward the colonization of thousands of new solar systems. 

Mankind spread quickly, soon populating more a region of space more than 1,000 light-years wide: the Inner Sphere.  As the human race spread, it brought with it the seeds of war.  The conquest of the Inner Sphere led to centuries of petty brushfire wars.

In 2571, humanity earned a respite from the tide of conflict.  The Star League, a new governing body, ushered in a golden age of prosperity and peace…

…a peace that was shattered by a bloody coup in 2767.

As the Star League fractured, each member of the ruling Star League Council declared himself the "rightful" ruler of known space, each laying sole claim to the Inner Sphere.

Dawn of the Successor States 

At the time of the Star League's collapse, human-occupied space was dominated by five interstellar empires, each ruled by a Great House, powerful dynasties that wielded vast military and economic power.  To this day, the Great Houses and their schemes and plots dominate the Inner Sphere.

Rise of the Clans 

When the Star League collapsed, the commander of its armies led millions of his soldiers on an exodus from the Inner Sphere, hoping to keep the ideals of the League alive.  The descendants of those original wanderers were tempered by harsh conditions, forged by a visionary leader into an unparalleled warrior society: the Clans.

In 3050, the Clans returned to the Inner Sphere, wielding advanced weaponry and superior military skill.  The Clans attacked without mercy, seizing hundreds of worlds and striking terror in the hearts of the citizenry. 

In 3058, the Great Houses of the Inner Sphere joined forces to create the Star League Constitution, a new version of the old and revered Inner Sphere government.  The new Star League was created for a purpose, however: to end the threat posed by the Clan.

In order to stave off the Clan threat, Inner Sphere forces led by Prince Victor Steiner-Davion launched a daring assault on the Clan homeworld of Strana Mechty.  Though many Inner Sphere MechWarriors died in the operation, the power of the Clan was broken, perhaps forever, by the skill and daring of MechWarriors!

From the Ashes 

No one expected the invasion of the Clans to work.  Most believed that the Clans would return to the Inner Sphere with Victor’s head on a pike.  History would prove them wrong.

But while Victor was intent on smashing the Clan threat, his sister Katrina (Katherine) Steiner, ruler of The Lyran Alliance, usurped Victor’s rulership and took control of the Federated Commonwealth. 

Katrina used the thinnest of legal precedents to seize Victor’s domain, angering many of the planetary dukes.  Duke Erik Scharpe was one of the few who dissented. 

Duke Scharpe - the ruling voice on Kentares IV - proudly claimed that his lord was Victor Davion and would remain so.  Others loyal to House Davion flocked to his banner.

Now the stage is set for a bloody civil conflict on Kentares IV, a flashpoint that may send all of the Inner Sphere into the fires of war…"

2235: Tamar Pact created

2271: Free Worlds League formed

2299: Federation of Skye formed

2315: Terran Hegemony formed

2317: Federated Suns formed

2319: Draconis Combine formed

2341: Lyran Commonwealth formed

2366: Capellan Confederation formed

2375: Robert Marsden named Archon Basileus

2376: Articles of Acceptance signed

2395: Robert Marsden assassinated, Alistair Marsden named Archon

2405: Alistair Marsden marries Katherine Steiner

2407: Tharkad named capital of Lyran Commonwealth

2408: Vega Strike enacted, Alistair Marsden killed, Katherine Steiner assumes Archonship

2412: Ares Conventions signed

2413: Brandenberg Edicts issued, Commonwealth Scout Corps formed

2439: BattleMech invented

2445: Katherine Steiner steps down, Alistair Steiner named Archon

2455: BattleMech plans stolen from Terran Hegemony

2463: Long March launched

2467: Alistair Steiner assassinated, Michael Steiner named Archon

2471: Michael Steiner dies, Steven Steiner named Archon

2488: LOKI incident

2501: Steven Steiner dies, Margaret Olsen named Archon

2503: Margaret Olsen removed

2506: Robert Steiner named Archon

2528: Robert Steiner abdicates, Craig Steiner named Archon

2543: Supreme Court of Commonwealth created

2555: Craig Steiner dies, Tracial Steiner named Archon

2558: Tharkad Accords signed

2570: Tracial Steiner dies, Viola Steiner-Dinesen named Archon

2571: Star League formed

2575: The Great Tax Debate

2581: Operation Mailed Fist launched

2591: Kevin Steiner-Dinesen kidnapped

2592: Kevin Steiner-Dinesen rescued, Estates-General disbanded

2596: Viola Steiner-Dinesen killed, Kevin Steiner-Dinesen named Archon

2611: Estates-General reconvened

2623: Businessman's Strike

2647: Kevin Steiner-Dinesen dies, Sarah Steiner-Dinesen named Archon

2660: Foreign tariffs rescinded

2672: Sarah Steiner-Dinesen abdicates, William Steiner named Archon

2704: William Steiner dies, Jonathan Steiner named Archon

2729: Jonathan Steiner dies, Michael Steiner II named Archon

2751: Simon Cameron killed

2760: Michael Steiner II dies, Robert Steiner II named Archon

2762: Richard Cameron comes of age

2765: New Vandenberg Crisis

2767: Amaris coup

2781: Star League dissolved, Robert Steiner II dies, Jennifer Steiner named Archon

2784: Operation Exodus takes place

2786: First Succession War begins

2791: Jennifer Steiner killed, Richard Steiner named Archon

2792: Reorganization of garrison

2812: Estates-General disbanded

2821: Peace Accord of Bella I signed, First Succession War ends

2822: Estates-General reconvened

2823: Richard Steiner dies, Marcus Steiner named Archon

2830: Second Succession War begins

2844: Marcus Steiner goes into a coma, Melissa Nin named Archon

2845: Marcus Steiner dies, Melissa Nin executed for treason, Claudius Steiner named Archon, 
Estates-General disbanded

2848: Operation Praying Mantis begins

2849: Claudius Steiner dies, Elizabeth Steiner named Archon-Designate, Estates-General 
reconvened, Triumvirate formed

2850: Yoguchi Kurita assassinated by Snow Fire

2859: Elizabeth Steiner named Archon

2864: Second Succession War ends

2866: Third Succession War begins

2895: Elizabeth Steiner dies, Eric Steiner named Archon

2908: Military Services Acts modified

2913: Operation Freedom begins, Eric Steiner killed

2914: Tatyana Steiner named Archon

2937: Tatyana Steiner abdicates, Marco Steiner named Archon

2952: Marco Steiner retires, Giovanni Steiner named Archon

2980: Giovanni Steiner dies, Alessandro Steiner named Archon

2987: Deep Raid of 2987

3002: Operation Concentrated Weakness begins

3007: Alessandro Steiner is forced to retire, Katrina Steiner named Archon

3020: Katrina Steiner issues Peace Proposal

3022: Federated-Commonwealth Alliance Document signed

3025: Third Succession War ends

3027: Operation Thor takes place

3028: Melissa Steiner marries Hanse Davion, Fourth Succession War begins, Unofficial creation of the Federated-Commonwealth

3029: St. Ives Compact formed

3030: Fourth Succession War ends

3034: Free Rasalhague Republic formed, Skye Crisis

3039: War of 3039 begins, Katrina Steiner abdicates, Melissa Steiner-Davion named Archon

3040: War of 3039 ends, Katrina Steiner dies

3041: Armed Forces of the Federated Commonwealth created

3050: Clans invade Inner Sphere

3052: Battle of Tukayyid, Hanse Davion dies

3055: Melissa-Steiner Davion assassinated

3056: Federated Commonwealth officially created, Ryan Steiner assassinated, Archon-Prince Victor Steiner-Davion takes control of Federated Commonwealth

3057: Lyran Alliance formed, Capellan Confederation and Free Worlds League invade Federated Commonwealth, Katrina (Katherine) Steiner-Davion named Archon of the Lyran Alliance.  Arc-Royal Cordon (Kell Hounds) formed along the common Lyran Alliance border with Clan Jade Falcon.

3058: Invasion of Coventry by Clan Jade Falcon.  Victor Steiner Davion comes to the aid of the Lyran Alliance with a multinational relief force and stops the invasion with diplomacy.  The Whitting Conference is held on Tharkad in November 3058 resulting in the rebirth of the Star League.  Sun-Tzu Liao named to post of First Lord.

3059: Victor Steiner-Davion leads force to shatter Clan Smoke Jaguar by launching a daring assault on the Clan homeworld of Strana Mechty.  Yvonne Steiner-Davion, the younger sister of Victor Steiner-Davion, is left as regent of the Federated Commonwealth (FedCom) in New Avalon.

3060: Overwhelmed with responsibility and manipulated by her sister, Yvonne Steiner-Davion abdicates rulership of FedCom to her sister Katrina (Katherine) Steiner-Davion.

3061: Prince Victor Steiner-Davion returns to the inner Sphere to find Katrina (Katherine) Steiner-Davion in command of the whole Federated Commonwealth.  Victor Steiner-Davion blocks his sister's attempts to become the next First Lord and is appointed as Precentor Martial of ComStar and Commander of the resurrected Star League Defense Forces (SDLF).  Animosity grows between the Federated Suns and the Lyran Alliance.  Protests mount against Katrina (Katherine) Steiner-Davion.

3062: While acting as 'peacekeepers' for ComStar in the disputed Lyons Thumb area of Lyran space, elements of the Draconis Combine 15th Dieron Regulars raid Skye.  Current First Lord and Combine Coordinator Theodore Kurita annexes the 8 worlds of the Lyran-controlled Lyons Thumb.

3063: House Steiner (elements of the Donegal Guards) invade the House Davion world of Kentares IV, once ruled by the formidable Duke Dresari.  Tensions and threats of open civil war between the former allies grow.  Young Duke Ian Dresari liberates Kentares.  Black Legion mercenaries stage a coup and retake Kentares from Ian Dresari for the Lyran Alliance Armed Forces (LAAF).