gearshift48
With about 10 shells the ship could muster enough explosive power to atomize all of the robots on the ground due to the fairly heavy explosive load that they carried, being atomic cluster shells. With the kinetic cannons of the robots, their shells wouldn't reach space and if they did, they'd be absurdly slow, for if they reached space in an elevated speed, they would likely also fuse the atoms of air inside of the barrel, causing an internal fusion nuclear detonation, which is never a good thing, the legion was cornered between ground and death.