"There are almost eleven shells 120mm of ISIS. This is like a prototype for the final product that was made at this factory," Muhsen Uqla, an artillery instructor with the Iraqi army told CCTV.

Factory is the right word for what the soldiers later discovered inside. Every single room in this large warehouse is a different step of an assembly line geared to mass-produce mortars that have a range of six kilometers.

The militants were making their bombs out of scrap metal, and used different molds. The manufacturing was on an industrial scale. Room after room, the Iraqi soldiers saw from tail fin assembly, to paint shop, and even a box of fuses to be screwed to the tips of the bombs.

The men who found the factory, said they had never seen anything like it.

"We've been in a lot of battles and we saw a lot of bomb factories in Fallujah, but this one is the biggest we have seen so far," said Uqla.

Mortars along with snipers and suicide vehicles are key components of ISIS' arsenal in Mosul.

"You see all those shells. They were supposed to be used against us. Thank god we captured them," said Uqla.

One arms factory is neutralized, but the soldiers have no doubt that there might be more ahead.

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