The Special Tasks Group (or STG) is the main espionage and military intelligence branch of the Seireitei. STG agents take part in performing dangerous stealth operations such as espionage, counterterrorism, infiltration, reconnaissance, assassination, black ops, and sabotage.
The Special Tasks Group forms most the the forces of Squad 9, as the squad and STG are one and the same. STG agents are trained to the bone to be practical, efficient, and deadly. They are trained to get the job done, no matter the risk to themselves or others. The mission is always first. STG agents are trained to be effective even with the most scarce of resources; being able to change tactics on the fly is a must.
On top of regular academy training, shinigami in the Special Tasks Group receive rigorous training over a one month period. In this time, the recruits skills are strained to the very limit. Their bodies and minds are tested until they snap. This is all to prepare them for a fight, torture, ruse, or whatever the battlefield may throw at them. STG training has become infamous for the three days at the end of STG training. During these three days recruits are subject to the most difficult scenarios one might face in the field. Recruits don't eat or sleep during these three days.