In other words my theory is that the blood oath that Dumbledore and grindelwald made was an oath just small step down from the unbreakable vow. if this is indeed so then it means such a pact can be broken but that it has either never been done before or the means were lost somehow. If so then dumbledore would have needed to devise a method. Doing so was not something any ordinary wizard could do but dumbledore's association with Flamel shows that he was no ordinary wizard. I think that dumbledore either had a means of breaking the oath or was in the process of devising one. If I'm right then that would be a feat that quite possibly eclipsed his longing for the deathly hallows. But having broken the oath and confronted grindelwald for their legendary duel dumbledore took the elder wand. But now dumbledore was many things he had not been before. he was bereaved from his sisters accidental death during the duel, he and his brother were estranged, his only real rival was vanquished and imprisoned in his own prison-like HQ, he possessed a wand of near limitless power, and he realized that he no long needed to remain on the sidelines. But a mind capable of devising a means of doing the near impossible eventually grows bored when returns to relatively mundane tasks. Dumbledore needed a new task and while offered "the top job" in the shape of minister of magic it was not a role he could trust himself with. He returned to Hogwarts instead and for a the time teaching satisfied him. He nevertheless thirsted for a new near impossible challenge besides teaching hormonal adolescents magic and self control. Shortly thereafter he came across tom riddle (brilliant, disturbed, a child born from a pairing that neither's ancestors would have dreamed of) and was both intriqued and disturbed by him. Riddle was invite into a world he'd suspected existed but never knew to be real. Riddle used his time there to become a consummate manipulator, silver tongue, and to search out any clue to whether his father had any magical parentage (having dismissed his mother for having succumbed to the fate of all beings, death). Only dumbledore knew riddle before this and was therefore forced to watch this dark awakening. Riddle graduated and used his charm and cunning to obtain objects into which he would transfer part of his soul (a process begone at hogwarts) in a bid for immortality. Each fragment (powerful and dangerous unto themselves) was protected and hidden behind yet more nefarious magic. When dumbledore found this out he had found a challenge even more insurmountable than the hallows and the blood oath. Finding and destroying these horcruxes would be challenge enough but riddle would almost destroy himself in attempting to take the life of a pure and innocent child whom would become perhaps the only second living horcrux (Harry Potter). Harry would later learn of his wizarding ancestry and would attend hogwarts. he would do well but would face challenges each year that he would never be to survive ordinarily but being a living horcrux who had somehow remained pure despite having a diabolical soul inhabiting his body would enhance his preexisting talents. he would be trained both by voldemorts other horcruxes and dumbledore himself into someone who would view it as his lifes mission to avenge his parents and riddles other victims by destroying riddles horcruxes and finally riddle himself. But a mere boy could never do this alone so dumbledore made potter want to learn from him directly. Dumbledore would train harry because potter had proven himself integral to any plan to destroy riddle and his horcruxes. Dumbledore's plan worked even from beyond the grave. Riddle gone permanently, the horcruxes destroyed, the deathly hallows united albeit never brought together with potter having revolved to have the elder wands power cease with him. Just the two greatest feats of magic and mind achieved and the only loser being dumbledore himself who was nevertheless dead and free to reunite with his family (except for his brother) and make his amends with them in the hereafter.

^ The best of essays.