Back in 1968, three Apollo 8 astronauts circled the moon on Christmas Eve and returned home, where they were greeted with a ticker-tape parade and honored on the cover of Time. Far out of sight from these public celebrations, however, another group of astronauts was training to reach space. Unlike the Apollo program, these spacemen were part of a clandestine military operation that had less to do with peaceful exploration of the heavens and much more to do with wreaking havoc in them.

One of those secret astronauts was retired Vice Adm. Richard Truly, who later headed NASA. “You just couldn’t tell anybody about it,” he recalled to me in 2007. “Nobody.” The details of the program—called the Manned Orbiting Laboratory (MOL) and run by the Air Force and the intelligence community’s National Reconnaissance Office (NRO)—were revealed last year when the NRO partly declassified more than 800 files and photos.

The project, which was in place from 1963 to 1969, aimed to spy on and thwart the Soviet Union in space. According to the declassified documents, one objective was to explore the feasibility of attacking Moscow’s satellites by knocking them out of orbit or firing projectiles at them. The program also included an elaborate plan to capture a Russian spacecraft in orbit, swaddle it in heat-shield material, and send it back to Earth for inspection. Yet despite Washington’s best efforts to keep these experiments under wraps at the time, its main adversary discovered the operation.

In fact, Moscow equipped its secret manned space station, Almaz, with a rapid-fire cannon, according to chief designer Vladimir Polyachenko. If a U.S. spacecraft attempted “to inspect or even attack the Almaz, we could destroy it,” Polyachenko told PBS in 2007. He also said that in 1975, cosmonauts test-fired the cannon, making the Soviet Union the first nation to weaponize an orbiting spacecraft.

For budgetary reasons, Washington’s MOL never got off the ground. Many of the astronauts transferred to NASA’s Space Shuttle program, but specifically to the clandestine side operated by the Air Force and NRO. Between 1982 and 1992, it conducted 11 shuttle missions that remain top secret.

China's space program. AP Photo / Xinhua, Zhao Jianwei

Given what operations were underway by the Air Force, it’s clear that foreign-satellite destruction was a high priority. In 1985, for instance, an Air Force pilot flying an F-15 fighter jet fired a missile at a failing U.S. satellite in low-Earth orbit. Until that day, no other country had annihilated a spacecraft with a weapon.

It would take 22 years before another power emulated that move: In 2007, Beijing launched a missile that demolished a Chinese weather satellite. Not to be outdone, Washington blasted another of its malfunctioning satellites the following year.

Back then, some might have argued that the space race had resumed. However, the NRO documents make it clear that the race never lapsed. They reveal that from its onset, the Space Age consisted of two very distinct parts: one in the spotlight, run by NASA, to explore the universe; and another in the darkness, run by the Pentagon, to militarize the universe. Today, NASA exists without a shuttle, pays Russia for rides, and wrestles with budget problems. Yet Washington continues to expand its secret space program—sending planes into orbit and developing satellites that have potentially offensive capabilities.

In 2001, a commission recommended that Washington “vigorously pursue the capabilities…to ensure that the President will have the option to deploy weapons in space.” A year later, President George W. Bush withdrew from the Anti-Ballistic Missile Treaty with Russia. In 2004, the secretary of the Air Force issued a document that codified its space-warfare policies and called for “space superiority,” which was defined as “freedom to attack as well as freedom from attack.”

While President Barack Obama vowed at the start of his first term not to militarize space, he did the opposite when he approved the launch of a number of military spacecraft that could double as both intelligence collectors and weapons systems. As recently as June, Gen. John E. Hyten, commander of the Air Force Space Command, issued a white paper that reiterated the push for “a force capable of achieving space superiority.” Coincidentally, circling above Earth at the time was an orbital test vehicle, the X-37B (of which the Air Force has two).

First launched in 2010, the unmanned plane is capable of remaining in space for up to two years at a time. Although the Air Force refuses to disclose the X-37B’s activities, its design is very similar in size, shape, and capabilities to the X-20 Dyna-Soar from the 1960s, which was crafted to be manned by a single pilot and to launch a nuclear weapon from space. Washington’s discreetness now has some—China, in particular—wondering whether the X-20 has come full circle in the X-37B.

The Air Force's X-37B. Wikimedia Commons

In June, Beijing debuted its own mysterious spacecraft into the galaxy. It is equipped with a long mechanical arm, ostensibly to scoop up space junk. But given the enormous amount of space debris and the maneuverability of the vehicle, some fear that its real purpose is to disable or destroy U.S. satellites in the event of a conflict.

To be sure, the more satellites spinning in space, the greater the chances that they collide, an accident that could be wrongly interpreted by an adversary. Of the roughly 1,300 active satellites, 568 are American—about 120 of which are military or intelligence spacecraft—more than double the number belonging to China and Russia combined.

One alternative to orbital calamity, of course, is orbital diplomacy. While the 1967 Outer Space Treaty bars the placement of weapons of mass destruction in orbit or outer space, it is silent on conventional weapons. The 1979 Moon Agreement bans the militarization of the moon and other celestial bodies, but it has not been ratified by the United States, Russia, China, or any other nation.

In 2008, China and Russia proposed an agreement to ban such arms. The U.N. General Assembly finally adopted a version of their proposal last December. The United States, arguing that the agreement is flawed and unverifiable, opposed it.

Without Washington’s buy-in, there is little incentive for others to adhere to the treaty. Other countries with military satellites in orbit, such as India or Israel, may also begin exploring defensive and offensive capabilities to protect their space assets.

Although Donald Trump said little about space during his campaign, he indicated plans to initiate a military buildup, which could very well include the cosmos. But he has a key question to answer: Is humanity better off with a celestial Wild West or with an orbital order, however imperfect?