A few months after the collapse of the Soviet Union, a group of American investors and Russian scientists struck a deal to begin marketing one of the crown jewels of Moscow's strategic arsenal: an entire family of missiles designed for launch from submarines.
Up for sale were powerful missiles called "Calm" and "Ripple," built to lob heavy warheads into space from a barge or a submarine tube, and a new model called "Surf" that could be rolled off the side of a ship and fired straight out of the water, according to The Washington Post.
The idea of the joint venture, as one of its US partners wrote in early 1993, was to link American satellite companies to a top Russian weapons laboratory to "convert potentially threatening submarine missiles into peaceful space boosters."
The Americans quickly ran aground on a series of legal and bureaucratic barriers, but the Russians forged ahead with a new partner willing to pay cash for Soviet military technology: North Korea.
More than two decades later, some of the Soviet designs are reappearing, one after another, in surprisingly sophisticated missiles that have turned up on North Korean launchpads over the past two years.
Now, newly uncovered documents offer fresh clues about the possible origins of those technical advances, some of which seemed to outside observers to have come from nowhere.
"The question that has long been raised is: Did North Korea get this technology from a [Russian] fire sale?" said David Wright, a missiles expert at the Union of Concerned Scientists.
"Did they get plans years ago and are just now at the point where they can build these things?"
North Korea is known to have relied on Russian parts and designs for its older missiles, including the Scud derivatives that had dominated its stockpile since the 1980s.
The newly uncovered documents include technical drawings for much more advanced missiles — designs that include features seen in some of the newest missiles in North Korea's expanding arsenal.
The documents from the Makeyev Rocket Design Bureau include marketing brochures for an array of top-of-the-line Soviet missiles that were able to deliver nuclear warheads to US cities.
Initially designed for the Soviet navy's nuclear submarines, some of the models offered for sale could be launched from a large boat, a submerged barge, or a capsule dropped into the ocean, negating the need for a modern submarine fleet.
"The missile could be floated and ignited without any need for a launch platform," recalled Kyle Gillman, the former executive vice president of the US-Russian joint venture known as Sea Launch Investors.
Gillman, who negotiated the business agreement with Russia's Makeyev scientists, reviewed and authenticated the documents obtained by The Washington Post.
The evidence that the designs eventually ended up in North Korea is partly circumstantial. In late 1992, with the US-Russian project flagging, more than 60 Russian missile scientists and family members from the Makeyev facility were arrested at Moscow's Sheremetyevo International Airport as they prepared to travel to Pyongyang to work as consultants.
US, Russian and South Korean intelligence officials later concluded that some of the scientists eventually succeeded in traveling to North Korea to offer blueprints and technical advice for the country's missiles program.
But US analysts see more persuasive evidence in the actual missiles that North Korea has put on display over the past two years.
In the most striking case, the Hwasong-10, or Musudan, a single-stage missile successfully tested by North Korea in June 2016, appears to use the same engine and many design features as the Soviet Union's R-27 Zyb, a submarine-launched ballistic missile designed by Makeyev scientists and advertised in one of the brochures obtained by The Post.
The fact that it has taken Pyongyang so long to exploit the Russian designs is perplexing, but North Korea had long lacked the sophisticated materials, engineering expertise and computer-driven machine tools for the kinds of advanced missiles it has recently tested, weapons experts say.
With an industrial base enhanced by years of slow, patient acquisition efforts, North Korea is only now in a position to capitalise on technology it had been sitting on for years or even decades, analysts say.
"North Korea was just recently able to acquire machine tools that were state-of-the-art in the 1990s, meaning they are still damn good machine tools," Wright said.
"Once you have the plans, and are able to get your hands on the materials and the right kinds of tools, you have a real leg up."
Helping Russians pay the bills
The US founders of Sea Launch Investors saw their joint project with the Russians as the profitable answer to two pressing global concerns, company documents show.
One was a shortage of launch capacity for a new generation of satellites servicing the rapidly expanding global telecommunications industry.
The other was the problem of newly idle weapons scientists in labs and factories across the former Soviet Union.
The abrupt halt to the Cold War in 1991 upended the careers of the thousands of physicists, chemists, microbiologists and engineers who built the Red Army's vast stockpile of nuclear, chemical and biological weapons, along with the missiles for delivering them.
Once among the elites of Soviet society, these highly skilled scientists faced an uncertain future with little meaningful work and a plummeting standard of living.
The United States would ultimately commit billions of dollars to help secure or dismantle Soviet weapons stockpiles and repurpose former weapons laboratories.
Yet, in the early 1990s, US officials remained gravely worried about the possible leakage of Soviet weapons secrets, and perhaps of the weapons themselves.
The Americans who founded Sea Launch Investors in 1992 believed that their project could help prevent the poaching of Russian weapons experts by terrorists and rogue states, at least from the community of rocket scientists at the Makeyev Rocket Design Bureau, the premier Soviet manufacturer of submarine-launched ballistic missiles headquartered in Miass, a small city in Russia's southern Ural mountains.
"We not only help the Russians to pay their bills and stabilise their country by showing them how the free enterprise system works," John E. Draim, a Navy pilot and engineer, wrote in the company's business plan in 1993, "but we also help those Americans who are looking for an economical way to get satellites into orbit."
In May of that year, a Protocol of Intent agreement was signed by retired Adm. Thomas Moorer, a former Joint Chiefs chairman and head of the American team, and retired Russian Adm. Fyodor Novoselov, a former deputy fleet commander for shipbuilding and armaments.
The joint venture acquired exclusive rights to Makeyev's inventory of submarine-launched ballistic missiles, and then developed marketing materials that showcased a line of products that could be converted for use in commercial ventures.
These included a missile known as the R-27 Zyb — or "Ripple" — the squat, blunt-nosed workhorse of the Soviet Union's Yankee-1 Class submarine fleet, along with larger, more powerful missiles such as the 50-foot-tall R-29 Shtil — or "Calm" — and the newer, solid-fueled R-39 Rif.
The latter two were true intercontinental ballistic missiles with a range of more than 5,000 miles.
But the marquee item was the Priboi, or "Surf," a hybrid model that the investors planned to create by combining parts of the Shtil and Rif into two-stage spacecraft designed to put small satellites into orbit.
The Surf's most extraordinary feature was that it could be fired into space without a submarine or conventional launchpad.
Using techniques that both the United States and Russia had developed experimentally in the 1960s and '70s, the missile could be launched from a floating tube, virtually anywhere in the world.
Here, Russian missiles had a distinct advantage, as their lower specific gravity allowed them to float vertically, like an ocean buoy.
Moreover, the engines for Soviet submarine missiles were specifically designed to ignite while their nozzles were still in the water.
Backers of the plan envisioned a day when Russia's missiles could launch commercial satellites into space quickly and cheaply, using a nearly infinite number of launch sites across the world's oceans.
"Erection in the water, even for the largest rockets, will take less than a minute," Draim wrote in the 1993 business plan. Telecommunications companies would save millions of dollars, he wrote, while eliminating a real threat to US national security.
Losing the peace
As the months passed, Makeyev's managers became increasingly frustrated as their American partners ran into a series of obstacles, including reservations about whether the joint venture was permissible under US-Russian arms-control agreements.
In April 1993, Gen. Colin L. Powell, then the Joint Chiefs chairman, informed Sea Launch Investors that the project could not proceed without a government review and a formal waiver of the Strategic Arms Limitation Treaty.
No waiver was granted, and by the spring of 1995, it was clear that the company was at a dead end.
"The present ground rules . . . practically put us out of business," Moorer complained in a memo on April 26 of that year.
By then, some of the Makeyev drawings and blueprints had apparently gone out the door.
The Russian scientists arrested at the Moscow airport acknowledged to investigators that they had been recruited as a group to assist North Korea in building rockets, ostensibly as space boosters for satellites.
In "The Dead Hand," David E. Hoffman's Pulitzer Prize-winning history of the last years of the Cold War, a Russian security official describes how the North Koreans systematically chose experts from across Makeyev's entire production line, from fuels specialists to engineers who designed the nose cone and payload chamber.
The salary offer, US$1,200 a month, was 200 times as much as some of the scientists were earning at home.
"This was the first case when we noticed the North Korean attempts to steal missile technology," the security official is quoted as saying.
Other attempts would follow. US and South Korean intelligence officials have confirmed that Makeyev scientists eventually did land jobs as consultants for the North Koreans, and technical drawings were passed to Pyongyang, either directly or through intermediaries.
Some of Makeyev's missile secrets appear to have left Russia before the joint-venture effort officially disbanded.
Still, years later, the company's former executive vice president remains convinced that most, if not all, could have been kept locked away if Western governments had acted quickly.
"We just needed to be creative, and try and win the peace," Gillman said. "But our government and military and intelligence agencies were shortsighted."
On June 22, 2016, North Korea successfully tested a mysterious new missile that differed dramatically from anything in Pyongyang's known arsenal.
The 36-foot-tall missile had a squat, snub-nosed frame and used a liquid propellent more powerful than the kerosene-based fuels the North Koreans had used in the past, potentially allowing it to fly farther, with heavier payloads.
The missile was dubbed the Hwasong-10, or Musudan. But experts noted striking similarities to the R-27 Zyb, or Ripple, manufactured by the Makeyev Rocket Design Bureau.
Two months later, on Aug. 24, 2016, North Korea successfully tested the Pukguksong-1, a submarine-launched missile that also incorporates some features from the Zyb.
Both models are "generally regarded as derived from the designs of the Makeyev Bureau's R-27," said Joshua Pollack, an analyst at the James Martin Center for Nonproliferation Studies in Monterey, Calif.
Those two tests were followed in recent months by even greater technological leaps, culminating in the successful tests this year of North Korea's first true intercontinental ballistic missiles, capable of reaching every city in the continental United States.
There have been no further tests of the Musudan, but satellite images released this month show that North Korea is building floating barges thought to be intended for tests of new submarine-launched missiles.
The construction is occurring in two different ports on opposite sides of the country.
US analysts also believe that North Korea is working on an improved version of the Pukguksong.
"I have to assume that Makeyev pitched part, if not all, of these concepts and proposals to other interested investors, including the North Koreans," said Michael Elleman, a former missiles scientist and a senior fellow at the International Institute for Strategic Studies, a British think tank.
While there is "solid evidence" that North Korea acquired blueprints for the R-27 Zyb, there is no proof so far that Pyongyang is building a clone of the R-29 Shtil, with its more powerful engine and 5,000-mile range. But Elleman cautioned: "It may be there, and appear in the future."