Mornbeast led his massive horde towards the Iron fortress, keeping their pace slow. He wanted the monsters to get as close as they could without alerting the soldiers at the fortress.
Suddenly, he heard alarms blaring, and he shouted to the monsters, "attack!"
From here, it was a complete onslaught of the fortress. Many of the flying monsters lept into the air and some of the faster ones charged at the walls to try and climb them. A massive, chubby monster launched itself at the huge gate, attempting to smash it with its large girth. It moved the gate, but it didn't break it by any means.
Mornbeast could hear shouting on the walls, and a thousand men were preparing themselves on the wall.
Little openings appeared within the walls of the fortress, and shots were being fired at any of the monsters attempting to climb up or fly over the walls.
Every single soldier on top of the walls was in an exosuit, and they fired down at the charging monsters.