[RossGmann]

Is the following site any help?
http://www.aeroflight.co.uk/waf/bulg...ve_history.htm

In part it states

Operation Tidal Wave, a massed air raid by American B-24 Liberators on 1 August 1943 was intercepted by Bulgarian fighters as it headed towards Romania. The Royal Bulgarian Air Force was now able to claim its first aerial victories, with Bf 109G pilots managing to bring down four B-24s. 14 November 1943 marked the start of a series of nine daylight air raids on the Bulgarian capital, Sofia. A late warning hindered the defences and only one escorting P-38 was shot down. Subsequent raids were heavier and involved aircraft from the Italian-based US 15th Air Force as well as the North African-based 9th Air Force. Bulgarian air defences became increasingly well organised, but despite fierce fighting could only bring down and average of 2% of the enemy raiders (39 aircraft in total) for the loss of 14 of their own. Eight night raids were also staged, but the lack of night fighters and night flying skills left aerial defence to the anti-aircraft artillery. After April 1944 the Allied bomber offensive returned to attacking Ploesti, with only sporadic air engagements occuring over Bulgaria.

Kind regards
Ross