Date: 202011
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Light: Night
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Tower ZZZ
Second aircraft: Commercial Fixed Wing
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Critical
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action
Contributing factors: Airport; Environment - Non Weather Related; Human Factors
Primary problem: Human Factors

Narrative: Company Flights Aircraft X (event flight) and Aircraft Y had all the elements in play for a severe collision during taxi operations at ZZZ airport; had it not been for the keen and alert awareness of the First Officer (FO) on our flight.Other Company Flight Aircraft Y had just landed on Runway XXC; exited onto Taxiway B; and received clearance to back-taxi on Runway XXR full-length and proceed to the gate. Shortly thereafter Aircraft X received taxi clearance to taxi to Runway XXC via Taxiway P; cross Runway XXR; left onto Taxiway G; and join Taxiway EX.Both flights were taxiing toward the intersection of Runway XXR and Taxiway P when it is assumed that Tower saw the potential collision as both aircraft had 'ALL LIGHTS ON' indicating that Aircraft Y was taxiing with clearance on an active runway; and Aircraft X was preparing to cross an active runway with proper clearance. Tower then attempted to modify the taxi clearance for Aircraft X but made an error by initiating the call with Aircraft Y's call sign. The transmission was unfortunately interrupted by a third aircraft trying to transmit as the Tower was attempting to correct the call sign; resulting in the amended clearance transmission being unintelligible to both Flights X and Y.Aircraft X was underway at a nominal taxi speed; and Aircraft Y was observed taxiing at a higher-than-normal speed as they back-taxied toward the turnoff point at the end of Runway XXR. Taxiway P enters at a slight angle preventing the Captain of Aircraft X from clearly seeing any approaching traffic from his right. As the Captain of Aircraft X; we had full intention of entering the intersection as initially cleared. Just prior I initiated a Safety call by saying 'Clear left.' At that point the FO looked right and said; 'Wow; they're moving fast; and don't think they're intending to stop.' Hearing that; I immediately began a full stop of our aircraft prior to crossing the hold short line; followed by turning our lights off; and yielding to Aircraft Y; in case we were the ones in error with the crossing clearance. Startled that we had just avoided a serious collision; we discussed the possibility of us missing a clearance or how that collision seemed inevitable had we not made the final 'Clearing check' prior to crossing the runway. Because of the frequency congestion with Tower working all three frequencies (Clearance; Ground; and Tower) and the fact that we didn't actually cross the hold short line; we held any immediate inquiry as to the miscommunication of the clearance to ourselves.Upon further discussion among ourselves after departure; we were certain that we did not miss any clearances from ATC and that this was a certain potential mishap that needed further investigation to acknowledge the chain of events from going unrecognized in the future.  We discovered that both aircraft had the appropriate clearance to be where they were and that there was an attempt by ATC to issue an amended clearance to us. Tower initially called Aircraft Y then quickly attempted to correct to Aircraft X; but the transmission was interrupted by a third aircraft rendering the call sign and amended clearance unintelligible for either aircraft to be warned appropriately about each other.Due to the angle to which Aircraft X was approaching Runway XXR; there wasn't a good line of sight for the Captain to see any approaching traffic back-taxing on Runway XXR until it would have been too late. It was only due to the vigilance and discipline from the FO in effectively communicating the immediate danger that we were we able to avoid a severe collision given the circumstances.It is believed that Tower was operating at reduced staffing levels even though there were a lot of aircraft movements at ZZZ that evening. This was likely due to COVID protocols in place with ATC. The increased workload enabled him to issue clearances to both Flight X and Y to be on Runway XXR at the same time if timing was ideal. In thiscase; an amendment to the clearance was attempted to be issued; however; time was not in our favor for the Tower to initiate the call with the wrong call sign and be interrupted by a third aircraft making the transition intelligible by either flight.




Synopsis: Air carrier Captain reported a near ground collision due to communication issues with ATC. Captain stated that Tower staffing levels may have contributed to the event.