The ongoing war in Ukraine reminds us that violence is endemic to human society, both at a large-scale, and at a micro-level.
The Buddha in his time knew this as much as anyone. He lived in an environment where smaller states were being invaded and gobbled up by larger ones. When the king of Magadha, Ajatasattu, invaded his neighbor Kosala, the Buddha openly sympathized with King Pasenadi’s efforts to defend his people, but only in a very limited, narrow way. He praised Pasenadi’s restraint in not just stopping Ajatasattu, but allowing him to live. In his words:
“A man may plunder as long as it serves his ends, but when others are plundered, he who has plundered gets plundered in turn.
A fool thinks, ‘Now’s my chance,’ as long as his evil has yet to ripen.
But when it ripens, the fool falls into pain.
Killing, you gain your killer.
Conquering, you gain one who will conquer you; insulting, insult; harassing, harassment.
And so, through the cycle of action, he who has plundered gets plundered in turn.”
A Battle (2), Saṅgāma Sutta (SN 3:15), translation by Ṭhānissaro Bhikkhu
Violence and aggression inevitably bring ruin to oneself. Glory in battle is something the Buddha also deflated quickly. The very best that could be said of violence is a means to stop other violence.
Thus, in the words of the Buddha in the Dhammapada:
131) Whoever takes a rod to harm living beings desiring ease, when he himself is looking for ease, meets with no ease after death.
132) Whoever doesn’t take a rod to harm living beings desiring ease, when he himself is looking for ease, meets with ease after death.
Dhammapada, translation by Ṭhānissaro Bhikkhu
This is true on a personal level as much as it is on a national level. A person who harms with words, actions or deeds others inevitably has to live in fear of the repercussions, and those repercussions are slow-burning and will came back worse.
Gleanings in Buddha-Fields 
