I have copied your question to the Kresy-Siberia Group in case somebody there can help. For example, Alex Topolski, group member and author of "Without Vodka", spent part of his life there before the war.
Anyway, here are my initial thoughts.
I assume that you are asking about the WW2 period regarding the Achtel's and Pruzany. This town, now in Belarus just north of Kobryn, was called Pruzana before the war and was in Poland's Polesie province.
Have you checked church and civic birth records for the Achtel family yet? You would have to write to Belarus to get them.
There is a "Children of Pruzany and Surrounding Area" website you may have already visited, at http://freepages.genealogy.rootsweb.com/~cpsa/general/cpsaind.htm where you could register your interest, although it does deal mainly with the town's Jewish population.
Regarding the OUN, I believe this was a bit too far north for the Ukrainian Nationalists to be active here.
You should explore the possibility that as catholic Poles, your family was deported to forced labour in one of the mass transports when the Soviet Union occupied this area in September 1939 under the Nazi-Soviet alliance. You can try to check with the Hoover Institution, which has partial records gleaned from the deportees saved by General Anders after the 1942 Polish-Soviet amnesty agreement. Here is the reference (and I have copied Irena Czernichowska of the Hoover to see if she can have a look for you for any Achtel family and secondly what the depositions have to report on what happened in Pruzana when the Soviets took over and incorporated it into the Belorussian SSR.)
Poland. Ministerstwo Informacji i Dokumentacji Records
REPORTS OF POLISH DEPORTEES, 1941
Box Folder Contents
Box 217. Polesie Province
- Folder 15 Pruzana City
- Folder 16 Pruzana County
Best of luck
From: "Edward Achtel" <achteles@...>
Date: Mon, 30 Dec 2002 10:11:24 -0600
I have an uncle, Antoni Achtel, who lived in Pruzany with wife Maria and eight children. He was the youngest of four brothers and originally from Stary Sacz. From family correspondence, I have the impression he was not very successful. I have been trying to get information on him and his family and on what may have occurred in the village of Pruzany, but without success. There appear to be people of Jewish origin with the name Achtel. My family roots are Roman Catholic to as far back (17th century) as I have been able to research. There were people by the name Achtel that were murdered by the OUN, but they were identified as Jewish and would not be of my family tree. Any information or advice regarding the above would be welcomed.
Respectfully, Edward Achtel at achteles@...