Question: Which military people served their allegiance to Union (American Civil War)?
SPARQL:
SELECT DISTINCT ?uri WHERE {?uri <http://dbpedia.org/property/allegiance> <http://dbpedia.org/resource/Union_(American_Civil_War)>  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/MilitaryPerson>}