The old king sighed, even if he moved he could not change the situation as the leaders of the orcs were waiting for him to do just that. And sadly he was outnumbered as the orcs had two warlords at Tier 10, leading the army.
Their hesitance in committing fully to the fight was thanks to the previous efforts of the kingdom. Having shown the might of the annihilation cannon, even having made it appear like there were multiple weapons at this level available to the kingdom.
And since the siege had started, the annihilation cannon had not made an appearance. Naturally, the orcs assumed that they were hiding it, waiting for them to move with a force that would be worth revealing its location.
For of course, once its location is known the orcs would focus to capture such a strong mobile weapon. While it can be partially protected by the magic towers, that was not enough if the warlords or Eight Claws targeted the cannon in earnest.