Bernard (Bernhardt?) Johansen from Oslo, Norway

Aloha! My maternal grandfather, Bernard Johansen was born on 10/11/1873 (approximately) in or near Oslo, Norway. Somehow arrived in America, joined American Army, met my grandmother(a native Hawaiian) married & started a family. We are now seeking more information about him as well as other relatives that may have come to America later. Are there any out there? His mother was Karen Poulsen (Paulsen?) and his father was Johan Carlsen(Carlson) as far as we know. Any help/leads would be greatly appreciated!!