The Buddha's path is the path to the end of suffering. Those on it should not take up arms or engage in violence with anyone, especially out of anger or hatred.
"When a warrior strives & exerts himself in battle, his mind is already seized, debased, & misdirected by the thought: 'May these beings be struck down or slaughtered or annihilated or destroyed. May they not exist': If others then strike him down & slay him while he is thus striving & exerting himself in battle, then with the breakup of the body, after death, he is reborn in the hell called the realm of those slain in battle. But if he holds such a view as this: 'When a warrior strives & exerts himself in battle, if others then strike him down & slay him while he is striving & exerting himself in battle, then with the breakup of the body, after death, he is reborn in the company of devas slain in battle,' that is his wrong view. Now, there are two destinations for a person with wrong view, I tell you: either hell or the animal womb."
— SN 42.3
Non-Buddhist statesmen and soldiers who engage in war must judge their moral decisions by other criteria and Buddhists should not criticize those who do not follow the Buddha by holding them to the Buddha's standards. However, I think it's clear that for a Buddhist, by the Buddha's standards,
there is no just war. Other people may have different standards and they will deal with the negative karma they accumulate doing so.
We should, with compassion, help these people to see the error of their ways, as the Buddha did with King Pasenadi. But in the end, it's not up to us. The best we can do is follow the Buddha's words and live harmlessly no matter what others may choose to do.
Gain and loss, status and disgrace,
censure and praise, pleasure and pain:
these conditions among human beings are inconstant,
impermanent, subject to change.
Knowing this, the wise person, mindful,
ponders these changing conditions.
Desirable things don’t charm the mind,
undesirable ones bring no resistance.
His welcoming and rebelling are scattered,
gone to their end,
do not exist.
- Lokavipatti Sutta
Stuff I write about things.