From "Manual of Muad'Dib" by the Princess Irulan

This knife will break then , Paul thought.
He cautioned himself that Jamis also was without shield, but the man wasn't trained to its use, had no shield-fighter inhibitions.
Paul stared across the ring at Jamis. The man's body looked like knotted whipcord on a dried skeleton. His crysknife shone milky yellow in the light of the glowglobes.
Fear coursed through Paul. He felt suddenly alone and naked standing in dull yellow light within this ring of people. Prescience had fed his knowledge with countless experiences, hinted at the strongest currents of the future and the strings of decision that guided them, but this was the real-now . This was death hanging on an infinite number of miniscule mischances.
Anything could tip the future here, he realized. Someone coughing in the troop of watchers, a distraction. A variation in a glowglobe's brilliance, a deceptive shadow.
I'm afraid , Paul told himself.
And he circled warily opposite Jamis, repeating silently to himself the Bene Gesserit litany against fear. "Fear is the mind-killer . . ." It was a cool bath washing over him. He felt muscles untie themselves, become poised and ready.
"I'll sheath my knife in your blood," Jamis snarled. And in the middle of the last word he pounced.
Jessica saw the motion, stifled an outcry.
Where the man struck there was only empty air and Paul stood now behind Jamis with a clear shot at the exposed back.
Now, Paul! Now! Jessica screamed it in her mind.
Paul's motion was slowly timed, beautifully fluid, but so slow it gave Jamis the margin to twist away, backing and turning to the right.
Paul withdrew, crouching low. "First, you must find my blood," he said.
Jessica recognized the shield-fighter timing in her son, and it came over her what a two-edged thing that was. The boy's reactions were those of youth and trained to a peak these people had never seen. But the attack was trained, too, and conditioned by the necessities of penetrating a shield barrier. A shield would repel too fast a blow, admit only the slowly deceptive counter. It needed control and trickery to get through a shield.
Does Paul see it? she asked herself. He must!
Again Jamis attacked, ink-dark eyes glaring, his body a yellow blur under the glowglobes.
And again Paul slipped away to return too slowly on the attack.
And again.
And again.
Each time, Paul's counterblow came an instant late.
And Jessica saw a thing she hoped Jamis did not see. Paul's defensive reactions were blindingly fast, but they moved each time at the precisely correct angle they would take if a shield were helping deflect part of Jamis' blow.
"Is your son playing with that poor fool?" Stilgar asked. He waved her to silence before she could respond. "Sorry; you must remain silent."
Now the two figures on the rock floor circled each other; Jamis with knife hand held far forward and tipped up slightly; Paul crouched with knife held low.
Again, Jamis pounced, and this time he twisted to the right where Paul had been dodging.
Instead of faking back and out, Paul met the man's knife hand on the point of his own blade. Then the boy was gone, twisting away to the left and thankful for Chani's warning.
Jamis backed into the center of the circle, rubbing his knife hand. Blood dripped from the injury for a moment, stopped. His eyes were wide and staring—two blue-black holes—studying Paul with a new wariness in the dull light of the glowglobes.
"Ah, that one hurt," Stilgar murmured.
Paul crouched at the ready and, as he had been trained to do after first blood, called out: "Do you yield?"
"Hah!" Jamis cried.
An angry murmur arose from the troop.
"Hold!" Stilgar called out. "The lad doesn't know our rule." Then, to Paul: "There can be no yielding in the tahaddi-challenge. Death is the test of it."
Jessica saw Paul swallow hard. And she thought: He's never killed a man like this . . . in the hot blood of a knife fight. Can he do it?
Paul circled slowly right, forced by Jamis' movement. The prescient knowledge of the time-boiling variables in this cave came back to plague him now. His new understanding told him there were too many swiftly compressed decisions in this fight for any clear channel ahead to show itself.
Variable piled on variable—that was why this cave lay as a blurred nexus in his path. It was like a gigantic rock in the flood, creating maelstroms in the current around it.
"Have an end to it, lad," Stilgar muttered. "Don't play with him."
Paul crept farther into the ring, relying on his own edge in speed.
Jamis backed now that the realization swept over him—that this was no soft offworlder in the tahaddi ring, easy prey for a Fremen crysknife.
Jessica saw the shadow of desperation in the man's face. Now is when he's most dangerous , she thought. Now he's desperate and can do anything. He sees that this is not like a child of his own people, but a fighting machine born and trained to it from infancy. Now the fear I planted in him has come to bloom .
And she found in herself a sense of pity for Jamis—an emotion tempered by awareness of the immediate peril to her son.