In the fictional BattleTech universe, the Sarna March was an administrative district of the Federated Commonwealth. The Sarna March was created after the Fourth Succession War out of the worlds the Federated Suns had conquered from the Capellan Confederation in the early 3030s and the worlds of the Tikonov Free Republic. Since Prince Hanse Davion had given the conquered worlds to his wife, Melissa Steiner, as his wedding present to her, the Sarna March was technically a part of the Lyran State Command. As such, the march was named after its capital world, Sarna, in the Lyran fashion.
The Sarna March was divided into two Operations Areas, Sarna and Terra Firma.
Joshua Marik, son of Captain-General Thomas Marik and heir to the Free Worlds League, was being treated at the New Avalon Institute of Science for leukemia in exchange for the Federated Commonwealth's ability to benefit from the League's large industrial base. When Joshua died, Archon-Prince Victor Steiner-Davion did not want to lose that support, so he executed a plan to replace Joshua with a body-double. This plan succeeded initially, but a Capellan spy was able to detect the fraud. This information passed up the chain until Chancellor Sun-Tzu Liao learned of it. Sun-Tzu decided to use this information to convince Thomas Marik to coordinate an assault on the Federated Commonwealth to regain territory they had lost in the Fourth Succession War.
Sun-Tzu had already been busy building up underground terrorist cells in many of the worlds of the Sarna March. In 3057, the Marik-Liao offensive began. The offensive was primarily spearheaded by Capellan terrorists and League mercenaries. Sensing her opportunity to seize power, Katherine Steiner-Davion, Victor's regent in the Lyran State Command, announced that she was enacting a little-known clause in the Federated-Commonwealth Alliance to secede the Lyran half of the realm from the Federated Commonwealth. She sent out a call to all traditionally Lyran units to return to within the nation's pre-Fourth Succession War borders and signed an independent truce with Thomas Marik. She called her "new" nation the Lyran Alliance.
The Sarna March ceased to exist around 3058, after the Lyran secession. Since the Sarna March was a part of the Lyran State, Archon Melissa Steiner had insisted on garrisoning it primarily with Lyran units. The Lyrans had used many JumpShips to return to Lyran space, leaving the remaining Federated Commonwealth units stranded and unable to help. Simultaneously, Capellan guerillas destabilized the planetary governments, but lacked the ability to fully conquer them without Free Worlds League support. This created a no-man's land that was dubbed the Chaos March.