Did Ashoka really become a Buddhist after a war?

The popular version goes like this: the emperor Ashoka won a bloody war, was sickened by what he had done, and turned to Buddhism. There is something in it, but the evidence is more tangled than that.

Ashoka was Emperor of Magadha from about 268 BCE. In his own words, carved on rock, he conquered the region of Kalinga in his eighth year on the throne. Rock Edict 13 says 100,000 men and animals were killed, many times that number perished, and 150,000 were carried off as captives, and it expresses his remorse for the slaughter. Yet the same edict is missing from his inscriptions in the Kalinga region itself, and one possibility raised by scholars is that the war's description is "more imaginary than real".

As for the conversion, the edicts suggest a gradual process rather than a dramatic one. In a Minor Rock Edict of his 13th year he says he had been a lay Buddhist for over two and a half years without much progress, and that in the last year he had drawn closer to the monastic community. The Sri Lankan tradition tells it differently, with a conversion in his fourth year, before the war.

Was he then a Buddhist emperor ruling a Buddhist state? He was a Buddhist: Minor Rock Edict 1 leaves no doubt that he followed Buddhism, and he calls himself a lay follower. But there is no evidence that Buddhism was a state religion, his own inscriptions do not mention doctrines like the Four Noble Truths or Nirvana, his edicts emphasise tolerance of all sects, and he donated caves to the Ajivikas, another religious group.