Irredentism
"Irredentism is any political or popular movement that seeks to claim/reclaim and occupy a land that the movement's members consider to be a "lost" territory from their nation's past. Wikipedia"
The event that thousands of English puritans arrived in Massachusetts bay as they fled persecution in England is the Great Migration, it was the movement of 6 million African-Americans <span>out of the rural Southern United States to the urban Northeast, Midwest, and West that occurred between 1910 and 1970.</span>
"<span>It led to a large number of causalities on both sides" would be the best option from the list, since the war still dragged on although now with far more men involved, meaning more deaths.</span>