Cixin Liu - Death's End

“Yes. The Staircase Program needed him. And now, my new plan does not need you. Both of you are very good, but you’re in the way. I have to advance, advance without regard for consequences.”

Another shot. The bullet went through the left side of Cheng Xin’s abdomen. She still didn’t feel pain, but the spreading numbness made her unable to keep standing. She slid down against the wall, leaving a bright trail of blood on the ivy behind her.

Wade pulled the trigger again. Finally, the passage of nearly three centuries caught up with the gun, and it made no sound. Wade racked the slide to clear the dud out of the chamber. Once again, he pointed the gun at Cheng Xin.

His right arm exploded. A puff of white smoke rose into the air, and Wade’s right forearm was gone. Burnt bits of bone and flesh splattered into the green leaves around him, but the gun, undamaged, fell to the foot of the building. Wade didn’t move. He took a look at the stump of his right arm and then looked up. A police car was diving toward him.

As the police car approached the ground, several armed police officers jumped out and landed in the thick grass waving in the turbulence thrown up by the propellers. They looked like slender, nimble women.

The last one to jump out of the car was AA. Cheng Xin’s vision was blurring, but she could see AA’s tearful face and hear her sobbing explanation.

“…faked my call…”

A fierce wave of pain seized her, and she lost consciousness.

When Cheng Xin woke up, she found herself in a flying car. A film clung to her and wrapped her tightly. She couldn’t feel pain, couldn’t even feel the presence of her body. Her consciousness began to fade again. In a faint voice that no one but herself could hear, she asked, “What is a Swordholder?”

Without a doubt, Luo Ji’s creation of dark forest deterrence against Trisolaris was a great achievement, but the Wallfacer Project that led to it was judged a ridiculous, childish act. Humanity, like a child entering society for the first time, had lashed out at the sinister universe with terror and confusion. Once Luo Ji had transferred control of the deterrence system to the UN and the Solar System Fleet, everyone thought the Wallfacer Project, a legendary bit of history, was over.

People turned their attention to deterrence itself, and a new field of study was born: deterrence game theory.

The main elements of deterrence are these: the deterrer and the deteree (in dark forest deterrence, humanity and Trisolaris); the threat (broadcasting the location of Trisolaris so as to ensure the destruction of both worlds); the controller (the person or organization holding the broadcast switch); and the goal (forcing Trisolaris to abandon its invasion plan and to share technology with humanity).

When the deterrent is the complete destruction of both the deterrer and the deteree, the system is said to be in a state of ultimate deterrence.

Compared to other types of deterrence, ultimate deterrence is distinguished by the fact that, should deterrence fail, carrying out the threat would be of no benefit to the deterrer.

Thus, the key to the success of ultimate deterrence is the belief by the deteree that the threat will almost certainly be carried out if the deteree thwarts the deterrer’s goals. This probability, or degree of deterrence, is an important parameter in deterrence game theory. The degree of deterrence must exceed 80 percent for the deterrer to succeed.

But people soon discovered a discouraging fact: If the authority to carry out the threat in dark forest deterrence is held by humanity as a whole, then the degree of deterrence is close to zero.

Asking humanity to take an action that would destroy two worlds is difficult: The decision would violate deeply held moral principles and values. The particular conditions of dark forest deterrence made the task even harder. Should deterrence fail, humanity would survive for at least one more generation. In a sense, everyone alive would be unaffected. But in the event of deterrence failing, carrying out the threat and broadcasting would mean that destruction could come at any moment, a far worse result than not carrying out the threat. Thus, if deterrence failed, the reaction of humankind as a whole could be easily predicted.

But an individual’s reaction could not be predicted.

The success of dark forest deterrence was founded on the unpredictability of Luo Ji as an individual. If deterrence failed, his actions would be guided by his own personality and psychology. Even if he acted rationally, his own interests might not match humanity’s interests perfectly. At the beginning of the Deterrence Era, both worlds carefully analyzed Luo Ji’s personality and built up detailed mathematical models. Human and Trisolaran deterrence game theorists reached remarkably similar conclusions: Depending on his mental state at the moment deterrence failed, Luo Ji’s degree of deterrence hovered between 91.9 percent and 98.4 percent. Trisolaris would not gamble with such odds.

Of course, such careful analysis wasn’t possible immediately after the creation of dark forest deterrence. But humanity quickly reached this conclusion intuitively, and the UN and the Solar System Fleet handed the authority to activate the deterrence system back to Luo Ji like a hot potato. The entire process from Luo Ji turning over the authority to getting it back took a total of eighteen hours. Yet that would have been long enough for droplets to destroy the ring of nuclear bombs surrounding the Sun and deprive humanity of the ability to broadcast their locations. The Trisolarans’ failure to do so was widely considered their greatest strategic blunder during the war, and humanity, covered in cold sweat, let out a held breath.

Since then, the power to activate the dark forest deterrence system had always been vested in Luo Ji. His hand first held the detonation switch for the circumsolar ring of nuclear bombs, and then the switch for the gravitational wave broadcast.

Dark forest deterrence hung over two worlds like the Sword of Damocles, and Luo Ji was the single hair from a horse’s tail that held up the sword. Thus, he came to be called the Swordholder.

The Wallfacer Project did not fade into history after all. Humanity could not escape the Wallfacers’ ghost.

Although the Wallfacer Project was an unprecedented anomaly in the history of humankind, both dark forest deterrence and the Swordholder had precursors. The mutual assured destruction practiced by NATO and the Warsaw Pact during the Cold War was an example of ultimate deterrence. In 1974, The Soviet Union initiated the Perimeter System (Russian Система «Периметр»), or “Dead Hand.” This was intended to guarantee that the Soviet Union possessed a viable second-strike capability in the event that an American-led first strike eliminated the Soviet government and high-level military command centers. The system relied on a monitoring system that gathered evidence of nuclear explosions within the Soviet Union; all the data was transmitted to a central computer that interpreted the data and decided whether to launch the Soviet Union’s nuclear arsenal.

The heart of the system was a secret control chamber hidden deep underground. If the system determined that a counterstrike must be launched, an operator on duty would initiate it.

In 2009, an officer who had been on duty in the room decades earlier told a reporter that at the time, he was a twenty-five-year-old junior lieutenant, freshly graduated from Frunze Military Academy. If the system determined that a strike was necessary, he was the last check before the complete destruction of the world. At that moment, all of the Soviet Union and Eastern Europe would likely be a sea of flames, and all of his loved ones above ground almost certainly dead. If he pushed the button, North America would also turn into hell on Earth in half an hour, and the following nuclear winter would doom all of humanity. He would hold the fate of human civilization in his hand.