Mars rules Aries and Scorpio, is exalted in Capricorn, in detriment in Libra and Taurus and in fall in Cancer. Ptolemy gives it a hot and dry nature, excessively so, and it is the lesser malefic, Saturn being the greater; it belongs to the nocturnal sect, which means that in the classical judgment it is somewhat better behaved in a night chart than in a day chart. Its natural significations are conflict, weapons, surgery, fire, iron, soldiers, competition, sharp instruments and sharp fevers, and anything cut, burned or forced. The classical texts do not present the malefics as simply bad; they are the planets of separation and reduction, and much of the practical art lies in judging their condition, sect, and relation to the benefics rather than in reacting to their presence.
Ptolemy's Tetrabiblos, part of the Hellenistic synthesis of roughly the first century BCE to the second century CE, gives a physical reason for Mars's assigned nature, stating that the planet dries and burns chiefly because of its fiery colour and its nearness to the Sun's own heat, the same proximity-based logic the text applies to every planet in turn. Mars's role as an omen-planet is considerably older than that synthesis, however, reaching back to Babylonian celestial omen-reading and horoscopy of perhaps 1000 BCE, where its reddish colour and irregular, sometimes retrograde motion made it a body of particular concern for omens of war and plague centuries before the Hellenistic apparatus of houses and aspects gave it the individual, chart-based malefic reading still used today.