They have massive particle accelerator cannons, laser rifles, combat mechs, hundreds of unmanned drones that can one-tap people, a dragon, and who knows what else.. Not a SINGLE shot was fired, they let them break through two walls with trebuchets for some reason, and then went straight to bows and swords.. Even basic-ass modern artillery has a range of like 30km+. They could've wiped out most of them before they even got anywhere near the city without a single casualty.. Or limit the bloodshed to an absolute minimum by drone striking the kings and generals, and going down the chain of command until they turn around and leave.. It's not like there's any downside or countermeasure..