After the bloody Kalinga war, to which religion did Emperor Ashoka formally convert and extend state patronage?

Introduction / Context:
The Kalinga war is a turning point in the life of Emperor Ashoka and in the history of ancient India. The large scale bloodshed and suffering reportedly transformed his outlook and pushed him toward a different religious and ethical path. This question asks which religion he embraced after the Kalinga war.

Given Data / Assumptions:
- The event in focus is the Kalinga war fought by Ashoka.
- The question is about the religion he adopted afterwards.
- The options include Jainism, Buddhism, Christianity, Judaism, and Zoroastrianism.

Concept / Approach:
According to inscriptions and traditional accounts, Ashoka became a follower and patron of Buddhism after the Kalinga war. He supported Buddhist monasteries, convened councils, and sent missions to spread the faith. The correct approach is to recall this well known historical fact and distinguish it from other world religions listed in the options.

Step-by-Step Solution:
Step 1: Remember that Kalinga was a major military campaign which caused immense loss of life and misery.
Step 2: Traditional narratives describe Ashoka as deeply moved by the suffering and seeking a more peaceful path.
Step 3: He turned to the teachings of the Buddha, embraced Buddhism, and promoted Dhamma policies reflecting Buddhist ethics.
Step 4: Compare this with Jainism and other religions that, while present in ancient India, are not associated with Ashokas personal conversion after Kalinga.
Step 5: Select Buddhism as the correct answer.

Verification / Alternative check:
An alternative check is to recall Ashokas role in spreading Buddhism beyond India. He is remembered for sending Buddhist missions to Sri Lanka and other regions, erecting stupas, and supporting the third Buddhist council. These activities confirm that his chosen religious path after Kalinga was Buddhism and not any of the other religions listed.

Why Other Options Are Wrong:
Option a is wrong because although Jainism was an important religion in ancient India, Ashoka is not known to have converted to Jainism.
Option c is wrong since Christianity arose later in West Asia and does not connect historically with Ashokas life.
Option d is wrong because Judaism is one of the oldest monotheistic religions but was not the religion adopted by Ashoka after Kalinga.
Option e is wrong as Zoroastrianism is associated mainly with ancient Persia and has no link to Ashokas conversion.

Common Pitfalls:
Students sometimes confuse Ashoka with other rulers who supported Jainism or mix up the roles of different religions in ancient India. Another error is to treat all ancient Indian religions as interchangeable. Paying attention to which ruler is associated with which faith helps prevent such mistakes.

Final Answer:
After the Kalinga war, Ashoka converted to and patronised Buddhism.