When I was thirteen, I was given a set of phylacteries with silver cases. They were decorated on each side with images of four Holy Land sites beaten in the silver. One of the sites was Rachel's Tomb near Bethlehem and of two I have no recollection whatsoever. The fourth, however, I remember distinctly. It was the Tower of David. Actually, it was what in modern times appropriated the title that had once belonged to another adjacent edifice. In reality it illustrated a seventeenth century minaret that had been constructed at the south-west corner of the fortress that is commonly referred to as the Jerusalem Citadel. A little irony then, for this sacred Muslim structure had become famous in its acquired role on items of Judaica, while the "real" Tower of David, a building that was the most substantial remnant of the three towers built by the king of Judea, Herod the Great in the first century BC, faded into oblivion (perhaps that is putting it a bit strong, for a monumental mass of stone can hardly fade).
The title - Tower of David, is of course an invention. King David had no connection to it, and despite some revisionist theories, the city in his time did almost certainly not extend as far west as Mount Zion. Herod had named the tower something else - either Hippicus or Phasael (a matter of dispute among scholars) the former being the name of a Herodian general and close friend of the king, the latter, his older brother. The link with King David appears to have originated either in Byzantine times (4th to 7th century AD) or subsequently during the period of Muslim rule when the tower was known as David's Prayer Niche (Miḥrāb Dāwūd محراب داود). In the eleventh century when Jerusalem was under Fatimid rule the David connection was given a rather remarkable boost when an old rival of that earlier Jewish king was also commemorated in the city's defences. During a major refortification of the walls, a new tower was built in the north-west just inside the wall at the corner of the city, and was named Burj or Qasr Jālūt - Goliath's Tower (برج جالوت/قصر جالوت).
Under the Franks the tower became much more than a fortification. It became a symbol of lay rule and its central position on the royal seal of the kingdom, dominating the two most important religious structures represented on either side of it - the Church of the Holy Sepulchre and the Templum Domini (formerly Dome of the Rock), should perhaps be seen as a visual rendition of the dominance, as perceived by the rulers of the crusader kingdom, of State over Church.
This role of the citadel as a symbol and indeed an implement of power, so much more important than its civic role, can be observed in a number of pivotal events in which it served to establish the identity of the ruler of the kingdom. Whoever held the tower ruled the kingdom.
The first of these events was when Jerusalem fell to the army of the First Crusade on 15 July 1099. One of the leaders of the crusade, Raymond of Toulouse, whose contingent had been stationed nearby on the southern part of Mount Zion, reached the tower first and promptly took hold of it, thereby de facto establishing himself as governor of the city, and potentially ruler of the kingdom that was about to come into being. He was, however, quickly dispossessed of the tower after Godfrey of Bouillon was elected as ruler. Initially Raymond stalled, claiming according to William of Tyre, that he wished to hold it only until the Easter passage, when he would return to Europe.* Godfrey, perhaps feeling that this was a ploy aimed at challenging his position of leadership, pressed for its immediate surrender. When Raymond's own men, many of whom wished to return home, supported Godfrey's demands he was forced to hand the tower over to Peter of Narbonne, Bishop of Albara, until a final decision was made. But, as William informs us, the bishop promptly handed it to Godfrey in what one imagines was a bit of back-handed political scheming. This solidified Godfrey's position and established the citadel as the supreme symbol of authority.
It was not long before the tower played the same role for a second time. This came in the wake of Godfrey's death on 18 July the following year. Godfrey had promised to the patriarch that on his death Jerusalem and its port, Jaffa, would be handed over to the Church. To forestall this and to make certain that lay rule continued over the kingdom and the Holy City, it was imperative that possession of the tower be kept out of reach of the patriarch, the powerful Daimbert of Pisa, and his supporters. Cleary, holding the Tower of David was viewed by all as a precondition to rule. A group of men faithful to Godfrey and intent on seeing his younger brother Baldwin of Boulogne inherit the rule, successfully prevented the patriarch from taking possession of the tower until Baldwin could arrive from Edessa.
The third time that possession of the citadel was central to a dispute over rule of the kingdom was in 1152, when Baldwin III wished to put an end to the joint rule with his mother Melisende that his minority had forced upon him. Melisende refused to hand over the reins of power and took refuge in the tower. It became vital for Baldwin to remove her from this symbol of rule and in order to do so he even brought siege machines into the city to bombard the citadel. Melisende was forced to withdraw to Nablus, and so for a third time possession of the citadel proved to be the precondition for establishing rule. This fact perhaps also lay behind the choice of location for the new royal palace that was built adjacent to the Tower of David a few years later.
* William of Tyre, Chronicon 9.3.