Flight Crew Air Transport Pilot (ATP)
Situational Awareness
ATC Issue All Types; Conflict NMAC
Flight Crew Took Evasive Action
Human Factors
Cleared for the visual approach to Runway 17R into OKC and was handed over to OKC tower. We checked in and were cleared to land 17R. I heard tower communicating with another aircraft that I could not hear. After recognizing a military call sign and became aware that they were on a HF frequency. Tower was advising him to remain in traffic for 17L as there was 'traffic for 17R'. A few seconds later he was advising them of traffic again for 17R and that it was a 'Aircraft X'. At this point I was trying to identify this aircraft as it was appearing to get a little out of hand between the tower controller and the military aircraft in the pattern. I identified the aircraft on TCAS as being at our 1130 to 12 o'clock and 300 feet below us climbing. At this point we are on final by the marker and we are trying to visually see the target. I look back at TCAS and the aircraft is 100 feet below us climbing and at 12 o'clock in close proximity. We receive a TCAS advisory to 'descend. descend; descend now!' We visually see this [military aircraft] coming at us and climbing but then leveling off at our altitude. I followed the RA as best I could as it appeared to be all red descending. It immediately then transitioned to a climbing command as we were closer to the ground than what was comfortable for a high rate of descent. We were in a Flaps 23 gear down configuration at this point. We were able to level off. [Military aircraft] remained at our 1 to 2 o'clock position and was communicating with tower but we could only hear towers instruction to him. Tower appeared to try and get him into the pattern again for 17L.We configured for landing and were in the configuration by 1000 feet and I think we were stable. We were stable for sure at 500 feet. [Military aircraft] remained at the 1 to 2 o'clock position and I was too focused on him and what he may do as he was still too close to us after this incident to be comfortable. I wanted to go-around to collect our thoughts as this incident was way too close 'for comfort' but I did not trust the actions of the [military aircraft] pilot after this incident as he was paralleling our course towards the runway and was trying to get back into the pattern so I felt it was safer to continue and land and we were descending on glide path to the runway and he was maintaining altitude upwind for the 17 runways.In summary we had a near miss on final approach to runway 17R in OKC which caused a TCAS RA. It commanded a uncomfortable descending RA within about 1500' of the ground followed by a climbing correction. We followed the RA as we were trained. I was the flying pilot and the autopilot was off. The [military aircraft] was close that the RA required me to bring power to idle and push hard over to initiate the RA. At no time did the Ground Proximity Warning System (GPWS) activate. We were stable on approach. We spoke with TRACON manager after landing and he advised that there were two military trainers in the pattern. There may have been some miscommunication between the aircraft and the tower controller. I made a PA at the gate advising the passengers of why the maneuvers on final and also the Flight Attendant heard very clearly the oral warnings as did some first class passengers.Appeared the military trainer entered final for our runway of 17R instead of 17L and when instructed to go around or re-enter the pattern he turned directly into our flight path and came directly at us.
[Report narrative contained no additional information.]
Air Carrier Captain on approach to OKC reported a NMAC with a military aircraft.