THE ACFT LANDED GEAR UP AFTER THE NORMAL AND EMERGENCY EXTENSION SYSTEMS FAILED TO EXTEND THE LANDING GEAR. DURING THE APPRAOCH TO LAND THE PLT NOTICED THE LANDING GEAR DOWN LIGHT'WOULD NOT COME ON'. A MISSED APPROACH WAS EXECUTED. THE PLTDISCUSSED THE PROBLEM VIA RADIO WITH A MECHANIC AND TRIED ALL EMERGENCY PROCEDURES TO LOWER THE NOSE GEAR WITHOUT SUCCESS. HE DIVERTED TO MANDAN VIA BISMARCK TO BURN OFF FUEL AND LAND WHERE HE COULD GET MAINTENANCE ASSISTANCE. THE PLTAND MECHANIC DECIDED THE ACFT SHOULD BE LANDED ON THE SOD WITH ALL GEAR UP AFTER ANOTHER ATTEMPT TO EXTEND THE GEAR FAILED. A FULL FLAP LANDING WAS MADE WITH ENGINES CUT PRIOR TO TOUCHDOWN. THE ACFT SLID 250 FT. EXAMINATION OF THE ACFT REVEALED THAT THE NOSE GEAR TORGUE TUBE WAS BUCKLED. INITIALLY IT WAS THOUGHT THAT A COOLING HOSE OR HEATER TUBE HAD INTERFERED WITH AND BUCKLED THE TUBE BY BEING IN THE WAY OF THE RETRACTION ROD. THIS WAS CONSIDERED BUT A MORE LIKELY REASON WAS OPERATION OF THE ACFT ON ROUGH TERRAIN.