In ancient times, walled cities were built to protect the citizens against marauding tribes and armies. As the city grew, additional concentric circles of defensives walls were built to enclose and protect ever-greater numbers of citizens. The cities came to resemble dartboards with rings surrounding a bull’s-eye.
If the city was attacked by an enemy army, the citizenry withdrew behind the outer ring of walls and defended themselves. If the outer wall was breached, the defenders withdrew to the next wall. If that walls was breached, they withdrew to the next wall, and so on, until they were forced back into the most heavily defended part of the city, the citadel. The citadel was the key of the survival of the kingdom. As long as it held, the city could be saved. The enemy could be beaten back and the kingdom rebuilt.
The citadel contained all the treasures of the city and was designed to accomodate the king, the top army officers, the leading citizens, and sufficient soldiers to sustain a prolonged siege. With adequate reserves, the city could survive until a neighboring kingdom sent an army to relieve the defenders.
