The Judah Initiative refers to a group of rabbis engaged in a secret war against the Thules. They continue to exist to the present, through the descendants of the original members. There is at least one known surviving rabbi, Aaron Bass.
During World War II, a group of Nazi occultist experimented on prisoners of war and Jews to master the art of necromancy, or reanimating the dead. This activities caught the attention of a group of rabbis, who planned to put a stop on the experiments of the Thules.
The Initiative then sent a golem to destroy the Thules. This proved most effective as the golem managed to kill all the Nazi soldiers save for their leader Eckhart, who escaped with a vanishing spell.
In 2013, the Initiative sought the lost ledger of the Thules. The ledger contained all the records of the Thules' experiments, regarding Necromancy. It was lost during the assault of the golem on the Thule headquarters. Aaron's grandfather successfully located the ledger and worked to protect it. Unfortunately, their enemy, the Thule Society also survived to the present, and was also looking for the ledger. The race to find the ledger resulted into the old rabbi's death, and to the transfer of responsibilities of the Initiative, as well as the possession of the golem, to Aaron. Simultaneously, the rabbi's death caught the attention of the Winchesters. The two hunters then aided Aaron in retrieving the ledger and fighting off the Thules.
Although the melee resulted in Aaron securing the ledger and securing his position as owner of the golem, there are still surviving members of the Thule society as Commander Eckhart's driver Heintz escaped. Moreover, it was revealed that the Thules managed to complete their experiments and began to reanimate their fallen allies.