Recently we were asked:
For participation of a specific ethnic group in Second World War in one specific country's forces, how do I construct the number? Is it possible to combine ethnic group and country? For example, how should Estonians in Waffen-SS be classified?
Winton Matthews, retired DDC assistant editor and currently a consultant, gave an answer that is adapted here:
An ethnic group associated with a specific aspect of a war (not just World War II) is classed with that aspect. If that aspect has its own number or is given in a class-here note, the ethnic group is shown by adding standard subdivision T1—089 Ethnic and national groups to the number for the aspect. The military units, air operations, and naval operations of a specific country in World War II have their own numbers at 940.5412 Military units of Allies, 940.5413 Military units of Axis Powers, 940.5449 Air operations of specific countries, and 940.5459 Naval operations of specific countries. Thus, standard subdivision T1—089 can be added. The number for Estonians in Waffen-SS is 940.54134308994545 Estonian participation in World War II army of Germany (940.5413 Military units of Axis Powers plus T2—43 Germany plus T1—089 Ethnic and national groups plus T5—94545 Estonians).
The add instructions for that last example are found at 940.54134-940.54139 Specific continents, countries, localities in modern world and T1—0891–0899 Specific ethnic and national groups. An example of a work classed in 940.54134308994545 is Estonian Vikings: Estnisches SS-Freiwilligen Bataillon Narwa and subsequent units, Eastern Front, 1943–1944.
Another example of a work treating participation of a specific ethnic group in one specific country's World War II forces is The Jewish Brigade: An Army with Two Masters, 1944–1945. That work is classed in 940.541241089924 Jewish participation in World War II army of Great Britain (940.5412 Military units of Allies plus T2—41 British Isles—"Class here Great Britain, United Kingdom"—plus T1—089 Ethnic and national groups plus T5—924 Jews).