From the back of the book:
"House Steiner has always been the unchallenged economic power of the Inner Sphere. Transformed from merchant-princes to a military juggernaut by years of war, the alliance with House Davion gave them the most powerful 'Mechs money can buy and a streamlined chain of command. Now, the Steiner-Davion alliance has fractured from within, threatening to engulf both nations in civil war.
BattleTech Field Manual: Lyran Alliance reveals the strengths and weaknesses of the new Alliance forces. This manual describes each Lyran regiment and its loyalties, profiles and special rules, plus cutting-edge equipment and the latest 'Mechs from the famed Steiner factories."