The seventh hexagram, Shi ("The Army"), places the trigram Kun (Earth) above Kan (Water). Water hidden within the earth is the image of a great mass concealed and held ready, like an army mustered among the people. It follows Conflict in the King Wen sequence, a natural pairing since disputes may harden into organized force.
Shi also holds a place in the xiantian, or Earlier Heaven, arrangement, the binary ordering devised by Shao Yong in the eleventh century and traditionally ascribed to Fu Xi: 48th of 64, quite apart from its seventh position in the King Wen sequence above. It was this Fu Xi ordering that the Jesuit Joachim Bouvet sent from Beijing in 1701 to Gottfried Wilhelm Leibniz, who recognized its broken and unbroken lines as his own binary 0 and 1.
Read from the bottom, the six lines of The Army run yin, yang, yin, yin, yin, yin. A later interpretive layer absent from the original Zhou Yi, the nuclear hexagram (hu gua), treats lines two through four as a lower trigram and lines three through five as an upper one; here they combine as Kun over Zhen, forming hexagram 24, Return (Fu), a hidden figure first associated with the Han-dynasty scholar Jing Fang, whose Yijing commentary of the first century BCE is credited with the earliest appearance of nuclear trigrams. The Army's King Wen partner is hexagram 8, Holding Together (Bi); most of the sixty-four pair this way, related by turning the whole figure upside down, while the eight hexagrams built from a single doubled trigram pair instead by inverting every line. Mawangdui (1973) orders hexagrams by trigram, not King Wen; names here follow Wilhelm and Baynes, 1950, not Legge, 1882.