This was the place to build a fortress against the darkness.

He has made an army and acquired the resources to build a fortress.

They appeared to be building fortresses out of their own bodies.

The new man was kind and did not feel the need to build invisible fortresses.

Building a fortress is another method of saving an otherwise lost position.

Yes, but then you end up building a fortress, not a building.

Why would they bother to build a new fortress at all?

You're helping them build a fortress that they will use against us.

After building a fortress they advanced towards the interior of the island.

In the 4th century the Thracians built a fortress there.