Zara went silent after Robin's gaze, she didn't know what to say anymore...
The battle taking place in the *Safe* City was made possible by the union of the Terra Beasts' Earth Seal Array and the Sky Seal Array. Without the two arrays, all these Martial Emperors and Ships would have dispersed each in a direction and the battlefield would have been the entire planet, or even outside of it, controlling them and making sure they were all killed before the information leaked would have been impossible.
Robin knew this, which is why he did not order the attack as soon as he felt the Truthful omen. Rather, he immediately went and modified the Heaven Seal Array that covered the entire central region, and then almost started another array to erect walls around the entire central region, but that bad feeling became unperable and forced him to start immediately.
