This scene, narrated by one of Arthur’s friends and warriors, Bedwyr (translating, I think, to Sir Bedivere), is from “Arthur”. Arthur and his men are prepared to do battle with an allied force of various barbarian tribes, but before the battle begins Arthur meets with the barbarian leader:
At [Arthur’s] use of the barbarian word for War Leader, the Angli glanced at one another. Then up spoke one of the barbarians “I am Baldulf,” he said, and his speech was not good. “What do you seek?”
“I seek peace,” replied Arthur, “which I gladly grant to you.”
Baldulf muttered something to one of his advisers, who muttered back. The Irish, of the tribe called Scotti, frowned mightily but said nothing.
“What are your terms?” asked Baldulf.
“You must leave this land. As you have done no harm here I will suffer no harm to come to you. But you must go from here at once.”
Again Baldulf conferred with his chieftains. Then, turning with a haughty sneer, he said “If we do not go?”
“Then you will all be killed. For I have given my promise to God that there will be peace in this land.”
Don’t fight if you can help it, but if you must, fight to win.