Pentagon, twin towers, and one other thing.
They taxed traders coming and leaving Ghana, and they used their armies to protect trade routes.
Answer:
Immigrants to work in steel mills
Explanation:
I don't know if I'm right, but it sounds like it. There was more immigration from Europe, so they must need those immigrants to take jobs at steel mills, to produce munition plants, and to work at stockyards. This is just my best guess.