 By November 1937, Colonel Gao's 4th PG had flown to Lanzhou Donggang Airbase where they were re-equipped with the Polikarpov I-16 Type 5, and then leading the second group in their return-flight to Nanjing on 21 November to resume combat operations.While refuelling at Zhoujiakou Airfield, they were caught by some Japanese ten Mitsubishi G3M2s, who evidently were conducting a reconnaissance mission.The bombs were already falling when Kao ran to his I-16.