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

With Gurney at my side . . .
Paul glanced down the ridge past the Fedaykin, studied the smuggler crew who had come with Halleck.
"How do your men stand, Gurney?" he asked.
"They're smugglers all," Gurney said. "They stand where the profit is."
"Little enough profit in our venture," Paul said, and he noted the subtle finger signal flashed to him by Gurney's right hand—the old hand code out of their past. There were men to fear and distrust in the smuggler crew.
Paul pulled at his lip to indicate he understood, looked up at the men standing guard above them on the rocks. He saw Stilgar there. Memory of the unsolved problem with Stilgar cooled some of Paul's elation.
"Stilgar," he said, "this is Gurney Halleck of whom you've heard me speak. My father's master-of-arms, one of the swordmasters who instructed me, an old friend. He can be trusted in any venture."
"I hear," Stilgar said. "You are his Duke."
Paul stared at the dark visage above him, wondering at the reasons which had impelled Stilgar to say just that. His Duke . There had been a strange subtle intonation in Stilgar's voice, as though he would rather have said something else. And that wasn't like Stilgar, who was a leader of Fremen, a man who spoke his mind.
My Duke! Gurney thought. He looked anew at Paul. Yes, with Leto dead, the title fell on Paul's shoulders .
The pattern of the Fremen war on Arrakis began to take on new shape in Gurney's mind. My Duke! A place that had been dead within him began coming alive. Only part of his awareness focused on Paul's ordering the smuggler crew disarmed until they could be questioned.
Gurney's mind returned to the command when he heard some of his men protesting. He shook his head, whirled. "Are you men deaf?" he barked. "This is the rightful Duke of Arrakis. Do as he commands."
Grumbling, the smugglers submitted.
Paul moved up beside Gurney, spoke in a low voice. "I'd not have expected you to walk into this trap, Gurney."
"I'm properly chastened," Gurney said. "I'll wager yon patch of spice is little more than a sand grain's thickness, a bait to lure us."
"That's a wager you'd win," Paul said. He looked down at the men being disarmed. "Are there any more of my father's men among your crew?"
"None. We're spread thin. There're a few among the free traders. Most have spent their profits to leave this place."
"But you stayed."
"I stayed."
"Because Rabban is here," Paul said.
"I thought I had nothing left but revenge," Gurney said.
An oddly chopped cry sounded from the ridgetop. Gurney looked up to see a Fremen waving his kerchief.
"A maker comes," Paul said. He moved out to a point of rock with Gurney following, looked off to the southwest. The burrow mound of a worm could be seen in the middle distance, a dust-crowned track that cut directly through the dunes on a course toward the ridge.
"He's big enough," Paul said.
A clattering sound lifted from the factory crawler below them. It turned on its treads like a giant insect, lumbered toward the rocks.
"Too bad we couldn't have saved the carryall," Paul said.
Gurney glanced at him, looked back to the patches of smoke and debris out on the desert where carryall and ornithopters had been brought down by Fremen rockets. He felt a sudden pang for the men lost there—his men, and he said: "Your father would've been more concerned for the men he couldn't save."
Paul shot a hard stare at him, lowered his gaze. Presently, he said: "They were your friends, Gurney. I understand. To us, though, they were trespassers who might see things they shouldn't see. You must understand that."
"I understand it well enough," Gurney said. "Now, I'm curious to see what I shouldn't."
Paul looked up to see the old and well-remembered wolfish grin on Halleck's face, the ripple of the inkvine scar along the man's jaw.
Gurney nodded toward the desert below them. Fremen were going about their business all over the landscape. It struck him that none of them appeared worried by the approach of the worm.
A thumping sounded from the open dunes beyond the baited patch of spice—a deep drumming that seemed to be heard through their feet. Gurney saw Fremen spread out across the sand there in the path of the worm.
The worm came on like some great sandfish, cresting the surface, its rings rippling and twisting. In a moment, from his vantage point above the desert, Gurney saw the taking of a worm—the daring leap of the first hookman, the turning of the creature, the way an entire band of men went up the scaly, glistening curve of the worm's side.
"There's one of the things you shouldn't have seen," Paul said.
"There's been stories and rumors," Gurney said. "But it's not a thing easy to believe without seeing it." He shook his head. "The creature all men on Arrakis fear, you treat it like a riding animal."
"You heard my father speak of desert power," Paul said. "There it is. The surface of this planet is ours. No storm nor creature nor condition can stop us."