Did Buddhism ever go through a period of relatively high violence?
Buddhism experience some very harsh periods. E.g. 


The destruction of Nalanda
Decline of Buddhism in India due to many factors
Kalinga Magha's invasion
Persecution of Buddhists


Buddhism would have gone through some violent times in the Malay Peninsula also as it was predominantly Buddhist before.

Following may also be interesting:


Decline of Buddhism in Thailand
Buddhism in the World Today