Why do they fight with knives and not with assault rifles in Dune?

Question

In the Dune series, especially in the movies, the fight scene involves combat with knives and daggers without use of energy weapons or "old-fashioned" assault rifles. Why?

Answer 1

It is because of the personal shield worn by warriors, except in the desert on Arrakis.

A slow moving object will penetrate a shield. A fast moving projectile will be blocked by it.

Paul grew up fighting wearing shields. On Arrakis the Fremen do not wear shields as they attract Sandworms. They only sometimes want to call a worm and use a thumper for the purpose.

I remember some important things about shields from the books. When Guerney is teaching a young Paul to fight wearing them he uses a famous phrase. "The slow blade penetrates the shield."

When Paul and Jamis are duelling to the death, Paul by habit strikes very slowly, he has no experience of fighting an opponent not wearing a shield. Also he has never killed a human being and is reluctant to do so. Stilgar misunderstood this at first and feared Paul was a sadist playing with a weaker opponent to be cruel before he kills him. Stilgar is very relieved when Jessica explains the true reasons for the way Paul fought.

A shield, if hit by a lasgun will cause feedback and a huge explosion of the lasgun and the shield both.

I will find you some quotes from the Dune books themselves.

“In shield fighting, one moves fast on defense, slow on attack,” Paul said. “Attack has the sole purpose of tricking the opponent into a misstep, setting him up for the attack sinister. The shield turns the fast blow, admits the slow kindjal!”Paul snapped up the rapier, feinted fast and whipped it back for a slow thrust timed to enter a shield’s mindless defenses. Halleck watched the action, turned at the last minute to let the blunted blade pass his chest. “Speed, excellent,” he said. “But you were wide open for an underhanded counter with a slip-tip.”

…

Jamis began sidling to the right along the edge of the ring opposite Paul. Paul crouched, realizing then that he had no shield, but was trained to fighting with its subtle field around him, trained to react on defense with utmost speed while his attack would be timed to the controlled slowness necessary for penetrating the enemy’s shield. In spite of constant warning from his trainers not to depend on the shield’s mindless blunting of attack speed, he knew that shield-awareness was part of him.

…

Lasguns would knock them down, but lasguns were expensive and notoriously cranky of maintenance—and there was always the peril of explosive pyrotechnics if the laser beam intersected a hot shield. The Atreides relied on their body shields and their wits.

The fact that feedback from a shield would explode both lasgun and shield did not bother the Harkonnens. Why? A lasgun-shield explosion was a dangerous variable, could be more powerful than atomics,

The Harkonnens surprise everyone when they do use old fashioned artillery on Arrakis.

THE BARON Vladimir Harkonnen stood at a viewport of the grounded lighter he was using as a command post. Out the port he saw the flame-lighted night of Arrakeen. His attention focused on the distant Shield Wall where his secret weapon was doing its work. Explosive artillery. The guns nibbled at the caves where the Duke’s fighting men had retreated for a last-ditch stand. Slowly measured bites of orange glare, showers of rock and dust in the brief illumination—and the Duke’s men were being sealed off to die by starvation, caught like animals in their burrows. The Baron could feel the distant chomping—a drumbeat carried to him through the ship’s metal: broomp... broomp. Then: BROOMP-BROOMP! Who would think of reviving artillery in this day of shields?