Did Buddhists ever actively participate in a major violent conflict?

The great "religions of peace" like Christianity and Islam had some quite turbulent events that seem in major conflict with their primary commandments, but still in the name of faith - even "within" (like bloody wars between catholics and protestants). Buddhism shuns all violence, but I'm curious how true to this philosophy did the believers remained through ages. Was there ever any major conflict involving violent confrontation, in which Buddhists would fight (violently, not passively) in defense of their religion? Are there any "shameful moments of Buddhism" like there are so many in other major religions?