The BLO was originally formed by four brothers as part of the Sinaloa Cartel and consisted largely of poppy and marijuana growers. Over time, the BLO changed its modus operandi and became muscle for the Sinaloa against the Gulf Cartel and its former military wing, Los Zetas.
In 2008, the Sinaloa and the BLO violently split. This conflict almost destroyed the BLO, as they were hounded by the Sinaloa and had to deal with arrests of their leadership and in-fighting amongst the upper ranks of of the organization. This weakness led the BLO to form pragmatic alliances with Los Zetas, the Knights Templar, and the Juarez Cartel in an effort to strike back against the Sinaloa.
The BLO is likely on the ropes. In October, Hector Beltran Leyva, the last of the original four BLO brothers, was arrested.