One of the greatest factors that led to massive emigration from ireland to the united states in the mid-1800s was

the best description of postwar writers might be progressive.

following the war, writers showed a tendency to work on artistic or social matters rather than political themes. while postwar literature may not have been the greatest period of english literature, the themes provided excellent critics a high number of novels. such examples include anthony burgess, anthony powell and frank kermode, all of which can be placed under the progressive view.

the answer to your question is

the treaty of hopewell