[Ger-Poland-Volhynia] Emmigration Pommern to Volhynia

[Marlo]

My husbands grandparents emigrated from the area of Pommerania, Stolp,
Lauenburg or Rummelsburg to area Volhynia, villages of Elisabethin.
Elzbiecin. I think the largest city near by was something starting
with Rosz---.
I know this isn't much but I wonder why they emigrated to Volhynia
around 1878.   My mother-in-law once told me they had to leave
Volhynia in 1888 or be killed. That's when they came to America and
settled in SW Michigan.  She never explained any more.  Can someone
help?
The information about Volhynia villages is out of the St. Petersburg
birth records.
Marlo