Wallfacer (3 Body Problem)

Wallfacers are a key element in Liu Cixin's science fiction series, Remembrance of Earth's Past, specifically the second novel, The Dark Forest. They are four individuals appointed by the Planetary Defense Council (PDC) to develop strategies against the Trisolaran invasion without needing to communicate their plans to anyone. Their power lies in the immense resources afforded to them and the absolute trust placed in their internal thought processes.

Due to the Trisolarans' ability to remotely observe human thoughts (via sophons, advanced subatomic computers), conventional strategic planning becomes impossible. Any revealed plan would be immediately compromised. Wallfacers are thus granted the freedom to conceive and implement strategies solely within their minds, acting as a "face the wall" to the enemy, their true intentions hidden from all, including the Trisolarans.

This freedom is not without risk. Wallfacers are given vast resources and influence based on their perceived potential to defend Earth. However, their strategies might be based on flawed logic, insanity, or even hidden agendas. Their actions are subject to scrutiny only after their implementation, leading to potential disasters if their plans are misguided.

The four original Wallfacers are Frederick Tyler, Manuel Rey Diaz, Bill Hines, and Luo Ji. Each Wallfacer approaches the threat in vastly different ways, some relying on scientific research, others on military strength, and still others on more abstract or psychological strategies.

A counterforce to the Wallfacers are the Wallbreakers. The Trisolarans select individuals to analyze and publicly expose the Wallfacers' true plans, effectively undermining their strategies. The battle between Wallfacers and Wallbreakers represents a crucial component of the psychological warfare in the Remembrance of Earth's Past series.