Smiley plays a small but pivotal role in "The Looking Glass War", le Carré's fourth novel, occupying the "North European desk" at the Circus. He appears sporadically throughout the book as a liaison to "The Department," a military intelligence agency, which attempts to surreptitiously conduct a dangerous and unnecessary operation without the Circus' knowledge. Smiley's appearance here is notable in that "War" is the only book of the series to depict his and Control's personal relationship in great detail. The climax of the novel bears witness to Smiley's ruthlessness, as he is dispatched by the Circus to end the Department's operation and force the abandonment of a Department employee to ameliorate the damage they have caused.