Theravada Buddhism is the dominant religious system in several parts of South and Southeast Asia, but there is a rich diversity of beliefs and practices in this tradition.
The Mahāyāna branch of Buddhism likely emerged around the first centuries A.D. and was most readily carried through the Silk Road and maritime trade routes.
In Theravada Buddhism, ordaining to be a monk and donating the merit thus gained is one of the greatest honors that a person can give to another - in this case to the Navy SEAL officer, who died.