Black May was the name given to a series of nerve agent attacks orchestrated against varying targets, mostly within the St. Ives Compact during the brief Capellan-St. Ives War in May of 3062. The attacks were orchestrated by Kali Liao, the sister of the reigning Chancellor of the Capellan Confederation, Sun Tzu Liao, as a means to bring a swift conclusion to the war. The plot was revealed by Kali to Sun-Tzu on the second of May, the day the attacks began. Realizing the implications of releasing a nerve agent during a war, Sun-Tzu Liao hurriedly informed Candace Liao, head of the St. Ives Compact, of what information the Maskirovka had extracted from Kali.
The warning came too late to stop the first wave of attacks. Making use of the same nerve agent that had been used to kill an entire battalion of the Nightriders regiment of McCarron's Armored Cavalry on Wei, members of the Thuggee cult targeted political and military targets within the St. Ives Compact. Notable casualties include Tormano Liao, the former head of Free Capella, General Simon Devon, a military liaison to the Compact from the Federated Commonwealth, and Tamas Rubinsky of the Rubinsky's Light Horse mercenary regiment, who survived the extensive lung and neural injuries but was left unable to pilot a BattleMech. An attempt was even made on Isis Marik, who was departing the Confederation after being dismissed by Sun-Tzu, but a Capellan escort destroyer neutralized the Thuggee JumpShip as soon as it entered the Necromo system.
The "Black May" attacks continued periodically from May 2nd to the beginning of June. In all, around 100,000 lives were lost to the "Black May" attacks; a diminuitive figure when compared to the 1,000,000 initially estimated. Sun-Tzu's quick thinking saved thousands of lives, but the political fallout from the sinister attacks only fueled resistance in the Compact and mired Confederation progress in the Capellan-St. Ives War.
As a direct result of the attacks, Kali Liao was imprisoned and sent to Atreus to stand before a war crimes tribunal composed of Captain-General Thomas Marik, Magestrix Emma Centrella, and a representative from the St. Ives Compact. Though she was dismissed on grounds of her insanity, Sun-Tzu would have her exiled to Highspire and supposedly disbanded her cult of Thuggee followers.