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

So these Fremen can handle 'thopters, too , Hawat thought.
On the distant dune, a Fremen waved a square of green cloth: once . . . twice.
"More come!" the Fremen beside Hawat barked. "Be ready. I'd hoped to have us away without more inconvenience."
Inconvenience! Hawat thought.
He saw two more 'thopters swooping from high in the west onto an area of sand suddenly devoid of visible Fremen. Only eight splotches of blue—the bodies of the Sardaukar in Harkonnen uniforms—remained at the scene of violence.
Another 'thopter glided in over the cliff wall above Hawat. He drew in a sharp breath as he saw it—a big troop carrier. It flew with the slow, spread-wing heaviness of a full load—like a giant bird coming to its nest.
In the distance, the purple finger of a lasgun beam flicked from one of the diving 'thopters. It laced across the sand, raising a sharp trail of dust.
"The cowards!" the Fremen beside Hawat rasped.
The troop carrier settled toward the patch of blue-clad bodies. Its wings crept out to full reach, began the cupping action of a quick stop.
Hawat's attention was caught by a flash of sun on metal to the south, a 'thopter plummeting there in a power dive, wings folded flat against its sides, its jets a golden flare against the dark silvered gray of the sky. It plunged like an arrow toward the troop carrier which was unshielded because of the lasgun activity around it. Straight into the carrier the diving 'thopter plunged.
A flaming roar shook the basin. Rocks tumbled from the cliff walls all around. A geyser of red-orange shot skyward from the sand where the carrier and its companion 'thopters had been—everything there caught in the flame.
It was the Fremen who took off in that captured 'thopter , Hawat thought. He deliberately sacrificed himself to get that carrier. Great Mother! What are these Fremen?
"A reasonable exchange," said the Fremen beside Hawat. "There must've been three hundred men in that carrier. Now, we must see to their water and make plans to get another aircraft." He started to step out of their rock-shadowed concealment.
A rain of blue uniforms came over the cliff wall in front of him, falling in low-suspensor slowness. In the flashing instant, Hawat had time to see that they were Sardaukar, hard faces set in battle frenzy, that they were unshielded and each carried a knife in one hand, a stunner in the other.
A thrown knife caught Hawat's Fremen companion in the throat, hurling him backward, twisting face down. Hawat had only time to draw his own knife before blackness of a stunner projectile felled him.
Muad'Dib could indeed, see the Future, but you must understand the limits of this power. Think of sight. You have eyes, yet cannot see without light. If you are on the floor of a valley, you cannot see beyond your valley. Just so, Muad'Dib could not always choose to look across the mysterious terrain. He tells us that a single obscure decision of prophecy, perhaps the choice of one word over another, could change the entire aspect of the future. He tells us "The vision of time is broad, but when you pass through it, time becomes a narrow door." And always, he fought the temptation to choose a clear, safe course, warning "That path leads ever down into stagnation."
—from "Arrakis Awakening" by the Princess Irulan
As the ornithopters glided out of the night above them, Paul grabbed his mother's arm, snapped: "Don't move!"
Then he saw the lead craft in the moonlight, the way its wings cupped to brake for landing, the reckless dash of the hands at the controls.
"It's Idaho ," he breathed.
The craft and its companions settled into the basin like a covey of birds coming to nest. Idaho was out of his 'thopter and running toward them before the dust settled. Two figures in Fremen robes followed him. Paul recognized one: the tall, sandy-bearded Kynes.
"This way!" Kynes called and he veered left.
Behind Kynes, other Fremen were throwing fabric covers over their ornithopters. The craft became a row of shallow dunes.
Idaho skidded to a stop in front of Paul, saluted. "M'Lord, the Fremen have a temporary hiding place nearby where we—"
"What about that back there?"
Paul pointed to the violence above the distant cliff—the jetflares, the purple beams of lasguns lacing the desert.
A rare smile touched Idaho 's round, placid face. "M'Lord . . . Sire, I've left them a little sur—"
Glaring white light filled the desert—bright as a sun, etching their shadows onto the rock floor of the ledge. In one sweeping motion, Idaho had Paul's arm in one hand, Jessica's shoulder in the other, hurling them down off the ledge into the basin. They sprawled together in the sand as the roar of an explosion thundered over them. Its shock wave tumbled chips off the rock ledge they had vacated.
Idaho sat up, brushed sand from himself.
"Not the family atomics!" Jessica said. "I thought—"
"You planted a shield back there," Paul said.
"A big one turned to full force," Idaho said. "A lasgun beam touched it and . . ." He shrugged.
"Subatomic fusion," Jessica said. "That's a dangerous weapon."
"Not weapon, m'Lady, defense. That scum will think twice before using lasguns another time."
The Fremen from the ornithopters stopped above them. One called in a low voice: "We should get under cover, friends."
Paul got to his feet as Idaho helped Jessica up.
"That blast will attract considerable attention, Sire," Idaho said.
Sire , Paul thought.
The word had such a strange sound when directed at him. Sire had always been his father.
He felt himself touched briefly by his powers of prescience, seeing himself infected by the wild race consciousness that was moving the human universe toward chaos. The vision left him shaken, and he allowed Idaho to guide him along the edge of the basin to a rock projection. Fremen there were opening a way down into the sand with their compaction tools.
"May I take your pack, Sire?" Idaho asked.
"It's not heavy, Duncan ," Paul said.
"You have no body shield," Idaho said. "Do you wish mine?" He glanced at the distant cliff. "Not likely there'll be any more lasgun activity about."
"Keep your shield, Duncan . Your right arm is shield enough for me."
Jessica saw the way the praise took effect, how Idaho moved closer to Paul, and she thought: Such a sure hand my son has with his people .
The Fremen removed a rock plug that opened a passage down into the native basement complex of the desert. A camouflage cover was rigged for the opening.
"This way," one of the Fremen said, and he led them down rock steps into darkness.
Behind them, the cover blotted out the moonlight. A dim green glow came alive ahead, revealing the steps and rock walls, a turn to the left. Robed Fremen were all around them now, pressing downward. They rounded the corner, found another down-slanting passage. It opened into a rough cave chamber.
Kynes stood before them, jubba hood thrown back. The neck of his stillsuit glistening in the green light. His long hair and beard were mussed. The blue eyes without whites were a darkness under heavy brows.
In the moment of encounter, Kynes wondered at himself: Why am I helping these people? It's the most dangerous thing I've ever done. It could doom me with them .
Then he looked squarely at Paul, seeing the boy who had taken on the mantle of manhood, masking grief, suppressing all except the position that now must be assumed—the dukedom. And Kynes realized in that moment the dukedom still existed and solely because of this youth—and this was not a thing to be taken lightly.
Jessica glanced once around the chamber, registering it on her senses in the Bene Gesserit way—a laboratory, a civil place full of angles and squares in the ancient manner.
"This is one of the Imperial Ecological Testing Stations my father wanted as advance bases," Paul said.