In
Medieval astrology a
besieged planet is a planet that is placed between two
malefic planets, namely Mars and Saturn. Besieged planets are believed to be very restricted in their functioning, so even if a planet is a benefic, the very fact that it is besieged means the beneficial attributes it would normally emanate will be lessened whilst in that configuration.
The term and concept of besiegement originally arose out of a concept in Hellenistic astrology called in Greek emperischesis or containment when a planet is hemmed in by two planets, either bodily or by their partile rays. A planet between the two malefics Mars and Saturn would be corrupted, while a planet between the two benefics Venus and Jupiter would be bonified, as long as no other planet interposes partile rays in the interval between the three planets.
Reference
http://en.wikipedia.org/wiki/Besieged_planet
