Who has fought in the conflicts around the Mississippi river?
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/property/place> <http://dbpedia.org/resource/Mississippi_River> . ?x <http://dbpedia.org/property/combatant> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/MilitaryConflict>}
Mississippi_River