Here's the section where the large scale use of motorized hang gliders is introduced:

Flint’s Huey swooped low over the harbor. Some movement to the left out of the overcast afternoon sky caught Flint’s attention, “What the hell is that,” Flint said to no one in particular, stabbing his finger at the western horizon out of the open side door of the helicopter.

Major Ramirez scratched the back of his neck under his fiberglass CVC helmet. Usually quick with an answer, he said, “It looks like a big flock of birds. . .” Rez squinted, “Is that more over there?”

Flint addressed the pilot over the mike attached to his CVC helmet. “Take us up a bit and fly closer to that,” he pointed.

Rez strained to see, then keyed his mike, “They’re not birds.”

The helicopter rose another 100 feet and edged west towards Chichin Island.

Flint was squinting too, “They’re too small and too slow to be fighters or helicopters. . .”

Rez’s voice cracked like a teenager’s, “Hell, they’re hang gliders. Motorized hang gliders!” Rez was amazed, not yet processing the military importance of what he was seeing.

Flint put out a net call designed to alert all Marines and even the now beached Curtis Wilbur and the Germantown to the new threat. Commander Meade beached his ship, Flint thought, he would have made a great Marine.

“Attention all Bulldog elements, all Bulldog elements. We are observing some motorized hang gliders coming in from the west. They are probably carrying light infantry. Estimated strength is two groups of ten to 15 gliders. They look like they can only carry one or two men. . .” Flint was about to request an acknowledgment of his transmission when he observed the low gray fog in the distance begin to resolve itself in to tiny specks. Flint keyed off the mike.

“Holy. . .” Ramirez muttered from behind his binoculars. He switched the intercom on and smacked Flint in the arm, “Sir, that fog bank over there is. . . What I mean is that. . .” The magnitude of what Rez was seeing prevented an easy description, “Damn it sir, it looks like the whole friggen PLA is riding in on motorized hang gliders. Can they do that?” Rez knew the question was silly and rhetorical. Rez remembered a small media report in 1999 or 2000 about the Chinese holding a military exercise in Tibet using motorized hang gliders, GPS devices and special communications equipment. He shrugged it off as a typically weird report from China. Certainly motorized hang gliders had no large-scale military utility.

Of course, that’s what the Western Allies thought in May 1940, just before German paratroopers conducted a massive vertical envelopment of Holland and executed the surprise capture of a formidable fortification in Belgium. Up to that time, the German (and Soviet Russian) preoccupation with sport parachute and glider clubs was deemed by some a healthy outlet for warrior-like impulses. Certainly, the experts thought, men dropped by parachute could do nothing more than serve as spies, scouts, or harassment forces. Having lost the last war, the Germans felt compelled to innovate. They proved the experts wrong.

After a few centuries of Western and Japanese domination, the Chinese similarly felt compelled to innovate. They knew it would be hopeless, at least in the short term, to match America and Japan dollar-for-dollar with high-tech equipment. But, if one was willing to accept something less than the state-of-the-art in the pursuit of military capabilities, then arriving at the use of motorized hang gliders in combat was a natural for the Chinese.

The Chinese recognized the utility of vertical envelopment. For years they maintained three airborne divisions (with plans to expand the force to nine), although they lacked the lift to send all three into combat at once (at least without pressing the civilian air fleet into service). Unfortunately, airborne forces could be used safely only when the enemy was not capable of downing a large number of them before they made it to the drop zone. For this reason, the Chinese became intrigued with the American concept of the airmobile division (first employed against China’s neighbor, Vietnam, in the mid-60s). Fielding enough helicopters to move an entire division, then training the division to fly and fight as a unit would be time consuming and expensive. Helicopters were also vulnerable to being shot down or bombed at their bases.

After years of thought and internal debate, the PLA decided on a third course in addition to the traditional airborne divisions. This choice was neither airborne nor strictly air mobile – they decided to create two divisions of motorized hang glider troops.

Each motorized hang glider cost the Chinese $500 to produce (the equivalent model sold for $10,000 retail in America). A few tubes of aluminum, some cable, some nylon and a motor-scooter motor and presto—a machine capable of carrying up to two soldiers 250 kilometers (150 miles) at a speed of 120 KPH (75 MPH) – fast enough to overcome the current 18 KPH headwinds in the Strait caused by the typhoon far to the south, but not fast enough to fly safely in rough weather.

To lift an entire division of light infantry (with some gliders carrying only one soldier and a heavy weapon or extra supplies) it took 7,500 gliders costing less than $4 million. The hang gliders were small and easy to operate. They were easy to conceal on the battlefield as they could be quickly disassembled and reassembled and they were almost impossible to shoot down en masse. Even if the enemy knew an attack was imminent, short of using a nuclear bomb, how could they down thousands of moving targets? Even their infrared signature was cool enough to avoid being acquired by heat seeking missiles. Add a few commercial GPS navigation devices for the platoon leaders and some lightweight communications equipment, and the force would know where it was and be able to send and receive orders. In the hands of the PLA, an army large enough to use it on a truly operational scale, the motorized hang glider was nothing short of a revolution in military affairs. It was perfectly suited to an infantry-rich and comparably low-tech army such as China’s. And, just as with Germany in May, 1940, the first widespread use of the tactic in combat was calculated to shock an unprepared enemy.