The Dark Forest

by Liu Cixin


The Trisolarians, an alien species from the Alpha Centauri system, look to colonize Earth due to the eventual inevitable destruction of their own planet. However, The Trisolarian invasion fleet will reach Earth in 400 years. Earth knows they're coming. To prevent Earth from mounting an effective defense, Trisolaris sent sophons, subatomic supercomputers, to monitor all activities on Earth, interfere with its efforts to research fundamental physics, and cripple its scientific development.


The Earth-Trisolaris Organization, a fifth column which worships the Trisolarians as gods, discovers that Trisolarian thought is transparently readable, and Trisolarians consequently have almost no concept of private thoughts or deceit. Trisolaris is threatened by the revelation that Earthlings do not have transparent thought and abandons the ETO when it is attacked by a military operation. The world’s governments obtain intelligence on Trisolaris from the operation.

Having been made aware of the Trisolarian threat, the United Nations appoint four “Wallfacers” to develop countermeasures. Each Wallfacer is given full access to the resources of the UN in order to plan secret grand strategies known only to themselves and prevent any Trisolarians or sympathizers from exposing their plans. The four Wallfacers selected are: former US Secretary of Defense Frederick Tyler; former Venezuelan President Manuel Rey Diaz; Nobel Laureate and neuroscientist Bill Hines; and, to general surprise, obscure Chinese sociology professor and former astronomy major Luo Ji. In response, Trisolaris locates and tasks remnants of the ETO to determine the Wallfacers’ plans. One “Wallbreaker” agent is assigned to each of Tyler, Rey Diaz, and Hines; Luo Ji is instructed by Trisolaris to be left alone, as he unknowingly holds a devastating truth that should not be revealed. Tyler and Rey Diaz’s plans are eventually exposed by their Wallbreakers and vetoed by the UN as being crimes against humanity. Tyler commits suicide; Rey Diaz is stoned to death by angry Venezuelans. An unwilling Luo Ji first abuses his power to live a hedonistic life, but is eventually forced to work. He comes to realize a universal truth and broadcasts the coordinates of a distant star as a test, but is almost killed by a genome-targeted flu released by ETO remnants to assassinate him and is placed in hibernation. Hines accidentally discovers a way to imprint an unshakeable belief into a person and builds a device to imprint Triumphalism into willing military members before also entering hibernation.

In China, Zhang Beihai, a Navy officer, is inducted into a nascent Human space force. He presents as a steadfast Triumphalist, and proposes that the space fleet of the future may be overwhelmed by Defeatism and be unable to confront Trisolaris. His superiors assign him and other Triumphalist soldiers with entering cryogenic sleep, to be awoken in the future when they are needed to reinforce Triumphalist sentiment in the space force. Before entering hibernation, Zhang secretly assassinates several medium drive researchers to ensure radiation drive research is prioritized. Scientists on Earth observe the Trisolarian fleet launching probes which will arrive before the fleet.

200 years later, Luo and Hines are awoken in an utopian society. Earth possesses three fleets, thousands in all, of ion-propulsion battleships faster than the Trisolarian fleet, and Humanity is collectively assured of its certain victory on Doomsday. The Wallfacer project is dismissed as crisis hysteria and terminated, but Hines’ wife reveals herself to be his Wallbreaker and reveals his plan: Hines was a secret Defeatist, and his device imprinted Defeatism instead of Triumphalism. Faced with the prospect of a secret Defeatist arm who may sabotage Earth’s success, Zhang and others are awoken and made acting captain over various battleships. Zhang takes the opportunity to hijack his ship and escape the solar system full-speed with all crew in tow; he was a secret Escapist who manipulated events to ensure the development of ships fast enough to leave the solar system. Four ships are sent after him in pursuit.

The first Trisolaris probe approaches the solar system, and in a show of strength, humanity launches 2000 warships to intercept it. The droplet-shaped probe is found to be held together by the strong interaction and suddenly activates; it quickly decimates the entire fleet by accurately ramming through each ship’s nuclear fuel cell. Two ships escape the battle and flee from the solar system together. Hearing of the defeat, the four ships chasing Zhang join him in his escape as one group. News of the defeat reach Earth and cause widespread panic; the droplet reaches Earth’s orbit and floods it with electromagnetic interference, preventing broadcasts from being sent out to the galaxy. Both groups of escaped spaceships attempt to head for distant star systems, but supplies are insufficient and suspicion mounts between ships. Eventually, one ship in each group preemptively bombards the others with anti-personnel bombs, killing the crews; they then scrap the derelicts for fuel and parts, and continue on their journey. Back on Earth, scientists realize the star whose coordinates Luo had broadcast 200 years ago had been destroyed.

The escaping ships and destroyed star give Luo proof of the truth he had realized: any spacefaring civilization must prioritize its own survival, and any alien civilization cannot be trusted to not exterminate your own civilization. Long interstellar distances make this suspicion impossible to dispel, so the best way to ensure one’s own survival is to stay silent (so as to remain undetected) and preemptively destroy any alien civilization one detects, akin to hunters stalking through a dark forest. Using this knowledge, Luo could threaten Trisolaris with exposing their location (and, consequently, the Earth’s) to the universe, but the evidence came too late; with the droplet in orbit, no broadcast of any sort can be released into the galaxy.

Years pass. Luo dedicates himself to the Snow Project, a futile effort using hydrogen bombs to scatter a debris field in a ring around the inner planets to detect when other probes arrive. He is shunned by the public for not having a plan to defeat Trisolaris, and descends into alcoholism. A shell of his former self, he travels to the grave of Ye Wenjie, the spiritual leader of the ETO and the person who hinted him toward the dark forest theory. There he digs a shallow grave, aims a gun at his heart, and issues an ultimatum to Trisolaris: he is wearing a dead man’s switch linked to 3614 hydrogen bombs in the Snow Project, and will commit suicide in 30 seconds. The bombs are strategically positioned so that when they detonate, the resulting debris fields will selectively block the Sun’s light and cause it to flicker in a specific pattern that encodes Trisolaris’ coordinates. Threatened with mutually assured destruction, Trisolaris sue for peace; they redirect their fleet to bypass the Solar System, stop droplet blockade of the Sun, and provide Earth with gravitational wave transmitter technology.