Operation Praying Mantis
The Death of the 4th Royal Guard
The elite House Steiner 4th Royal Guards regiment, nicknamed The Pride of Commonwealth, was garrisoned on the Lyran Commonwealth world of Caledonia in anticipation of a Draconis Combine Mustered Soldiery invasion. The Kurita attack force led by Hugai Kurita, son of then Coordinator Yoguchi Kurita, struck in 2841 and was successful enough to establish a beachhead, though commander of the 4th, Colonel Tiber Hinders, felt sure that his troops could push the invaders back. For the next seven years the conflict dragged on as every attack and defensive move the 4th made was countered, and caused Hinders and his brother Michael to suspect a spy in their midst. With the aid of the spy and Archon Claudius Steiner's preference towards blood sports and the torture of his own internal enemies rather than Hinders and the Lyran Commonwealth Armed Forces' pleas for aid, the elite 4th Royal Guard was utterly destroyed in 2848.  
In celebration of his victory, Hugai offered the captive Hinders the chance to duel against the spy who'd destroyed his regiment. Leaping at the chance, Hinders and the spy received battered and weaponless Thunderbolts, smashing and battering each other as the Kurita forces watched. Suffering from radiation poisoning, a desperate Hinders was eventually able to defeat his foe, and pulled open his opponents cockpit to see his brother Michael's body. Though nobody knows if he really was the spy or just part of game played by the sadistic Kurita, Hugai "humanly" dispatched the despairing Colonel Hinders with a laser blast, making sure to record and send the event to Claudius Steiner.  
Enraged as much by Hugai's insult as much as the loss of an elite regiment, Claudius sent a coded message to Snow Fire, a female deep-cover Lyran Intelligence Corps agent serving as a geisha on the Kurita capital of Luthien, with new orders and information on the sadistic destruction of the 4th.   
With no hesitation given her final fate, Snow Fire spent a year and half steadily advancing her standing in the Imperial Palace and attempting to attract the eye of the Coordinator himself. She was successful and became Yoguchi's favorite concubine, when Yoguchi left the capital to personally lead the defense of Tishomingo. Thought killed, Yoguchi survived in secret and was eventually extracted. On his first night back on Luthien, Snow Fire quietly slit his throat with a plasticine knife. After placing a hand embroidered patch of the House Steiner 4th Royal Guard on his body, Snow Fire took her own life with poison secreted in a hollow tooth.    
The death of Yoguchi so soon after his miraculous return shook the Draconis Combine, while Claudius Steiner never lived to see Praying Mantis come to fruition, dying himself under clouded circumstances in 2849. Publicly, Combine propaganda put forth the idea that Yoguchi was killed while heroically fighting a whole team of assassins, but the House Kurita inner circle felt great shame in the very concept that a lone Lyran spy could get so close undetected and assassinate the Coordinator. Yoguchi's successor, his brother Miyogi, felt honor-bound to avenge this insult which lead to the largest Kurita offensive against the Lyran's center of 'Mech production Hesperus II and the loss of the last active Successor State WarShips until the arrival of the Clans.    
That Snow Fire was able to remain undetected whilst sending secret information to her "mother" lead to a large and varied array of conspiracy theories about how she was able to complete her mission. Some point to ComStar shielding the messages from House Kurita, lent credence due to the later knowledge ComStar actively fanned the flames of the Succession Wars. Others point to Yoguchi's alienation of the ISF, placing the organization under the command of the DCMS, allowing his murder as the climax of a shadow war against him.    
The fact that her true love was apparently a member of the destroyed 4th Royal Guard lent her actions the air of tragic romance and helped inspire endless countless paintings, dramas and ballads about celebrating her actions and possible origins across the Inner Sphere.    
- House Steiner (The Lyran Commonwealth), p. 61 - "Death of the Fourth - Operation Praying Mantis"
- Handbook: House Steiner, p. 43 - "History of the Lyran Alliance - Second Succession War (2830-2864) - The Mantis Strikes"
- House Kurita (The Draconis Combine), p. 70 "History - Second Succession War - The Sting of Snow Fire - Divine Retribution"
- House Davion (The Federated Suns), pp. 73-74 "History - Second Succession War - Tishomingo - Did Snow Fire Have Help? - Miyogi's Marathon"