Maybe this will be interesting to note. Some soviet pilots that had to fight hard in Spain published their memories. But only Boris Smirnov book related about first downed Messerschmitts during the Brunete battle. Despite his precise description of that battle (especially with the R-Zet), he described it as a big aerial fight over Madrid sky on 8 July 1937. But he wrote it many years on a old age, after a long service in the VVS, fighting also in Mongolia, and WWII. In his books he usually shows great precision and technical science with the description of the dogfights but he is often faulty with dates. Two possibilities: either he never participated in the battle of the 12, either and it is the more credible* he describes the first victory on a bf 109 by Piotr Burtym, a zveno commander from the 116th iae MVO. Bounced by MOSCAS of the Chevtsov escadrilia, G Honess had not time to run away as its colleagues an was soon (easily) outmaneuvered and shot down by the soviet pilot.
As Burtym succeeded to fire on the pilot at a shorted distance, the Messerschmitt immediately went down from a 2500m height and crashed in the nationalist area.
On the same day, (it has nothing to do about our story, but might be interesting) a Tupolev SB was shoot down over Segovia in a recce mission suppository by Rolf Pingel. The pilot and navigator were maid POW, and gunner MIA. The were condemned to death and survived to several simulated executions before they were exchanged in 1939 and returned back to USSR.
Another sole SB was pursuit by two fiat on a recce mission over the port of Palma. This time it suddenly turned back and boom-zoomed Italians fighters itself! Back at the airbase the crew claimed a victory on 1 "fiat".
Probably very embarrassed, nationalists 'till that day begun night intruder missions over Republican territory. It's all for the 12.