Sargon probably perceived Urartu as a weak target following the news of Rusa I's defeat against the Cimmerians. Rusa was aware that the Assyrians were likely to invade his kingdom and had probably kept most of his remaining army by Lake Urmia following his victory over the Mannaeans as the lake was close to the Assyrian border. Because the kingdom had been threatened by the Assyrians before, the southern border of Urartu was not entirely defenseless. The shortest path from Assyria to Urartu's heartland went through the Kel-i-šin pass in the Taurus Mountains. One of the most important places in all of Urartu, the holy city Musasir, was located just west of this pass and as such it required extensive protection. This protection was to come from a series of fortifications and during his preparations for Sargon's attack, Rusa ordered the construction of a new fortress called the Gerdesorah. Though the Gerdesorah was small, measuring about 95 x 81 metres (311.7 x 265.7 ft), it was strategically positioned on a hill about 55 metres (180.4 ft) higher than the rest of the terrain and had 2.5 (8.2 ft) metre thick walls and defensive towers. One weakness of the Gerdesorah was that it had not yet completely finished construction, only starting to be built c. mid-June of 714 BC.