If I may, I will offer some comments and resources by Buddhist teachers from a few traditions on this ...
In a 2014 essay, Ven. Bhikkhu Bodhi, wrote:
The Buddha’s discourses give us glimpses into the tumultuous tide of the era. They tell how “men take up swords and shields, buckle on bows and quivers, and charge into battle… where they are wounded by arrows and spears, and their heads are cut off by swords… and they are splashed with boiling liquids and crushed under heavy weights” (MN 13:12–13). ... Against this backdrop of social chaos and personal disorientation, the Buddha propounded an ethic of harmlessness that rejected violence in all its forms, from its collective manifestation in armed conflict to its subtle stirrings as anger and ill will. He rested this ethic on the appeal to empathy, the ability to imagine oneself in the place of others: “All beings fear violence, all fear death. ... But while the ethic of harmlessness may have served well as a guide to personal conduct, the governance of a state presented a moral quandary, with which the texts occasionally grapple. ... In time of war, I would argue, the karmic framework can justify enlisting in the military and serving as a combatant, providing one sincerely believes the reason for fighting is to disable a dangerous aggressor and protect one’s country and its citizens. Any acts of killing that such a choice might require would certainly be regrettable as a violation of the First Precept.
Thanissaro Bhikkhu wrote a strong rebuttal, and then there was a back and forth of debate:
http://www.inquiringmind.com/Articles/B ... tters.html
The arguments in “War and Peace: A Buddhist Perspective” by Bhikkhu Bodhi (Spring 2014) are deeply disturbing to anyone committed to living by the Dhamma. Because they muddy the waters around the issue of killing and because confusion on this issue leads to harrowing consequences
In my own viewless view (as one Practitioner), abiding by the Precept to Preserve Life and Avoid the Taking of life, it may be necessary to take life to save other lives and to restore peace. I feel that the Suttas and Sutras offered many opinions on these questions (having been written, of course, by men of many opinions), and modern teachers are of many minds on this. However, Buddhist voices disagree.
From the opinions of Buddhist teachers from various traditions which I have read, I would say that almost all who saw the need for some response involving the taking of life saw it as a "necessary evil" ... not as a path or goal in any positive sense. Sometimes we must break a Precept to keep a Precept. And given modern warfare, most of the teachers were aware that this might include the unavoidable taking of civilian and other "non-combatant" lives in order to save a much greater number of lives.
I believe that the following responses, some by the Dalai Lama, are representative of the diversity of opinion.
(the comments which follow are also very interesting)
http://www.tricycle.com/feature/war-or- ... de-the-box
Thich Nhat Hanh seems to be more representative of the "any violent response only leads to increased violence" opinion ...
http://www.pbs.org/wnet/religionandethi ... hanh/1843/
The Buddha also seems to have been of two minds on this. On the one hand, there are some writings in which he is framed to say that killing is never skillful.
http://www.accesstoinsight.org/lib/auth ... ssage.html
On the other hand, in other Sutta he did seem to countenance a nation having an army for certain limited purposes, and its discreet use.
also (although on the following, I have some doubts about the author.
(by the way, a very interesting story about the author of that piece, but I am wondering if the author had any role in the violence in Sri Lanka. Does anyone have further information: http://www.sundayobserver.lk/2007/05/13/fea06.asp
Almost all the Buddhist teachers I can think of (including me too, for what it is worth) would say that we must also bear all the Karmic consequences of our volitional words, thoughts and acts, no matter whether we had a "reason" for killing or not.
You may kill the cat, but you still likely have to pay the price in some way.
A Tibetan teacher (Chagdud Tulku) relates this famous Jataka legend about a previous incarnation of the Buddha ...
(In a previous life, the Buddha was Captain Compassionate Heart, sailing with 500 merchants. An evil pirate, Dung Thungchen (Blackspear) appeared, threatening to kill them all. )The captain, a bodhisattva himself, saw the [pirate]'s murderous intention and realized this crime would result in eons of torment for the murderer. In his compassion, the captain was willing to take hellish torment upon himself by killing the man to prevent karmic suffering that would be infinity greater than the suffering of the murdered victims. The captain's compassion was impartial; his motivation was utterly selfless.
I am not sure about the effect of our Karma in lives to come ... but I do know that we likely will bear the effects of our actions in this life in some way. I have a friend, an ex-policeman, who had to kill someone in a perfectly necessary and justified act to save lives. Yet, my friend still carries that with him to this day.
No, taking lives is never a "good" thing.
It is important to remember too that Buddhists do not generally believe in "bad people", only in "people who do bad things" because they themselves are victims of greed, anger and ignorance within. The real evil doer is "greed anger and ignorance".
Even if one is required to act in self-defense ... of one's own life, the life of another, or to protect society as in the case of a policeman or soldier ... one should best not feel anger even if forced to use force
, one should nurture peace as much as one can, avoiding violence as much as one can, using violence as little as one can even when needed.
Yes, most all flavors of Buddhism teach that, even should one be forced to break a Precept in a big or small way, one should bear the Karmic weight, reflect on having had to do so, seek as one can not to do so in the future.
The case I usually mention is that friend of mine, a Buddhist policeman, who had to kill someone in the line of duty in order to save an innocent person held hostage. It was a perfectly justified, necessary shooting. However, from that day he always felt a kind of mental scar, a heavy weight ... even though he knew he had to do the right thing. He always felt the need to bring peace into the world in some measure to make up for what he had had to do. So it is for all of us if we must reluctantly support the use of violence in order to preserve life.
Let me close with something recited by us in our Sutra Dedication ...
We dedicate our hopes and aspirations:
To all victims of war and violence and natural events
To the injured and to all families touched by these tragedies
To the healing of hatred in all countries and among all peoples
To the wisdom and compassion of our world leaders
To the peace of the world and harmony of all beings.