Frelsesarmeen

I've been working on tracking one of my wife's relatives. In the course of that search I came upon this record: http://digitalarkivet.arkivverket.no/en-gb/ft/person/pf01037045119144 It lists her "religion" was Frelsesarmeen which I understand is the Salvation Army in Norway. Does anyone know of any history of what the Salvation Army was doing in Norway at this time and why she might have put that as her religion? For background, the woman I'm looking for - Anna (Annie) Opsal - immigrated to the US in 1915 and settled in Northfield MN as a housekeeper. She later married Per Algot ("Algot Pearson" in the US) and died in 1972 in Northfield. Thanks!