Sentence:  Was it supposed , perchance , that A + M ( vocational training , that is ) was quite sufficient for the immigrant class which flooded that part of the New England world in the post Civil War period , the immigrants having been brought in from Southern Europe , to work in the mills , to make up for the labor shortage <WSD>caused</WSD> by migration to the West ? 
Meaning of the word marked with <WSD> tags:  give rise to; cause to happen or occur, not always intentionally