A planet is besieged when it lies between two malefics, or when, having separated from a malefic, the next aspect it makes is with a malefic. Traditionally, a planet is besieged if it lies between Mars and Saturn and in the same sign with them, for example, Mars at 22° Pisces, Sun at 24° Pisces and Saturn at 27° Pisces, seen in my son's chart. The word "besieged" means surrounded or crowded in by hostile forces, these being in this case Mars (enemies; conflict; passion) and Saturn (restriction; sorrows; karma), who are surrounding, crowding and assailing the Sun (inner self; individuality). Besiegement in a birth chart is usually overcome by progression, but still remains a basic vibration.