Outnumbered and Outgunned, the Bulgarian Air Force Battled the Allies Over Sofia
Bulgarian pilots flew secondhand French fighters
In April 1941, Bulgaria was drawn half-heartedly into World War II by Nazi Germany. Adolf Hitler threatened Bulgaria with invasion if it didn’t allowed German troops to invade Greece and Yugoslavia through Bulgarian territory — and, if the kingdom cooperated, promised to give it Greek and Yugoslav territory in Thrace and Macedonia.
Bulgarian nationalists had long claimed these regions belonged to a Greater Bulgaria, so the kingdom let the Germans march through — and received its promised cut of territory. Owing to the populace’s pro-Russian sentiment, Bulgaria refused to participate in the invasion of the Soviet Union two months later. However, its troop did assist the Nazis in their brutal campaigns to crush Yugoslav partisans.
Six days after the attack on Pearl Harbor in December 1941, Bulgaria — compelled by its alliance with Germany — declared war on the United States. Washington didn’t bother reciprocating until June 5, 1942 — making Bulgaria among of the last three countries the United States ever formally declared war on!
The obsolete Avia B.534 biplane was the Royal Bulgarian Air Force’s most numerous fighter. The air arm also flew 19 Messerschmitt 109E fighters. By 1943, the massive U.S. 9th Air Force had massed hundreds of four-engine heavy bombers in the Mediterranean. The Bulgarians realized they needed cannon-armed, high-altitude fighters to have any chance of shooting down the heavy bombers.
Nazi Germany had just confiscated 276 Dewoitine D.520 fighters from Vichy France. It offered to send 150 to Bulgaria. First, the kingdom’s pilots traveled to Nancy, France to receive flight training from German and French pilots on the ins-and-outs of handling the temperamental D.520.
German fighter pilot Wolfgang Fischer recounted his experience in his memoir Luftwaffe Fighter Pilot:
I have to admit that this French fighter was the only aircraft that I ever actively disliked. It had none of the good-natured qualities of the Messerschmitt and was an altogether malicious beast. Take your eyes of the airspeed indicator for a single second, dare to drop a fraction below minimum speed and — without the slightest warning — the Dewoitine would immediately stall, tip over on to its left wing and whip into a spin.
Admittedly recovery was not all that difficult, but it required a good 1,000 meters to get it back on an even keel. It also had a mind of its won on the ground, and taxiing was an art in itself. The mainwheel airbrakes were controlled by two separate pushbuttons and a pilot’s inexperience could be judged by the amount of drunken weaving about he did as he taxied to and from dispersal.
The Bulgarians proved themselves to be extremely competent fliers, however — although their individualistic behavior, not to say downright indiscipline in the air left a lot to be desired.
In August 1943, the German flier shepherded his students as they ferried their fighters from France to Bulgaria. The mischievous trainees over-turned a sailboat while buzzing Lake Balaton, and treated Fischer to a raucous, all-night vodka binge after landing in Bulgaria.
Ultimately, 96 to 98 Dewoitine 520s made it over to Karlovo air base in Bulgaria. However, three French instructors defected en route during the transit and instead landed in Switzerland.
In September 1943, the 6th Fighter Regiment held a public ceremony to celebrate the fighter’s arrival. The unit’s 1st, 2nd and 4th Orliak — wings — all flew the type, though the 4th saw little action. The Royal Bulgarian Air Force also received 23 German Messerschmitt 109G2 fighters at this time. These served in the 3rd Orliak. Upgraded with new 1,475 horsepower Daimler Benz 605A engines, the German fighters now possessed a notable edge over their former French rivals.
Another important acquisition was the German Freya-LS and F radars that gave Bulgarian fighters early-warning capability. However, the RBAF as a whole suffered severe serviceability problems, with as little as 40 percent of its force available to fly at any given time.
On Aug. 1, 1943 153 B-24 Liberators hit the Ploesti oil fields in Romania as part of Operational Tidal Wave. Lacking fighter escort, the bombers sustained 33-percent losses to flak and German and Romanian fighter planes.
On their return journey, the American bombers passed over Bulgaria, where 21 outdated B.534s and 14 of the new Messerschmitts intercepted them. The latter aircraft succeeded in shooting down four American bombers in their first aerial combat of the war.
A B-24 flying over a burning oil refinery at Ploesti in Romania on Aug. 1, 1943. U.S. Air Force photo
Air war over Sofia
On Oct. 20, 1943 Winston Churchill informed Allied commander Gen. Dwight Eisenhower he should take “hard measures” to neutralize the Balkans’ contribution to the Axis war economy, including petroleum, copper and aluminum.
In Bulgaria, the railway station in the capital of Sofia would become the main target. The extraordinary imprecision even of daytime raids — with 80 percent of bombs falling more than a thousand feet off-target — guaranteed heavy collateral damage to the surrounding city.
According to historian Nickolay Georgiev Kotev, “demolition of Sofia was considered necessary because the city was deemed a crucial communication center and a vital link of the Axis supply system in the entire southeastern Europe.”
The D.520 squadrons weren’t ready for action when the first major raids hit Sofia in November 1943. Messerschmitts failed to react in time to intercept an attack by 91 B-25 medium bomber on Nov. 14, but shot down two Liberator bombers out of 60 on a raid on Nov. 24, disrupting the attack. One Bulgarian fighter was lost to escorting P-38 Lightning fighters.
Note that there are discrepancies on exact losses for each engagement, and this account leans toward figures from Air Power of the Kingdom of Bulgaria IV by Dimitar Nedialkov.
Bomb damage in Sofia
The Dewoitines finally engaged the enemy on Dec. 10, 1943. Twenty-four of the fighters, backed up by 17 Messerschmitts, scrambled from Vrajdebna and Karlovo to intercept 120 U.S. bombers and fighters. However, the Bulgarian fighters were late and disorganized in their interception. Capt. Pavel Pavlov’s Dewoitine was shot-up in a head-on attack and crashed, killing Pavlov. No enemy aircraft were shot down.
Realizing they needed to improve their tactics, the Bulgarian fliers practiced coordinating their attacks, and on Dec. 20, 1943 they successfully mustered 16 Messerschmitts and 24 Dewoitines to face 100 B-24 bombers and Lightnings. The Messerschmitts of the 3rd Orliak engaged the Lightnings at 6,000 meters, while the Dewoitines of the 2nd Orliak drove for the bombers.
In the ensuing melee, they shot down seven P-38s and three B-17s. Dimitar Spisarevski, flying his first combat mission, rammed his Messerschmitt into the tail of a B-17 above the village of Dolni Pasarel, killing himself and destroying both aircraft. One other Messerschmitt was lost.
In early 1944, the RBAF began receiving 85 additional Messerschmitt 109G-2s and G-6s, and converted some of its D.520s units to the German fighter. However, the U.S. 9th Air Force also deployed new drop-tank-equipped P-51 and P-47 escort fighters that were more effective dogfighters than the P-38 was.
280 Flying Fortresses and P-38s blasted Sofia in a daytime raid on Jan. 10, 1944. Thirty-eight Dewotines 520s and Messerschmitts loaded with anti-aircraft rockets harried the enormous formation with hit-and-run attacks. They shot down six of the four-engine bombers and three P-38s, losing just one D.520.
Bulgarian pilot Petar Petrov recalled the battle in his memoir, in a passage translated by Krasimir Alexandrov in Mushrooms #6115.
Our 2/6 Orliak on Jan. 10,  took off in full establishment of 32 Dewoitines. Arranged in a column of fours we climbed to the west. We were at about 7,000 in when we saw the Fortresses. As we were on the approaching course, we went in the frontal attack, like on Dec. 20, [1943.]
None of us trembled, and none moved away from the steel avalanche approaching us with huge speed. Everyone took one Fortress in the gun sight and waited for the moment to push the trigger on the machine guns and cannon. None of us paid attention how we retreat after the attack.
Wing by wing we came near the Fortresses. We saw how they moved up-down, left-right. They were upset by our attempt to scatter them with frontal attack. All in this moment was for seconds — take aim at the last moment, open fire and move away back from the attack in any possible way for everyone. One was running into the battle, another exited by semi looping, third aside and up.
The effect of our frontal attack was great — the first group of bombers deviated from the attack, dropped their bombs on a field, without taking the battle course to the heart of Sofia.
B-24 over Sofia. U.S. Air Force photo
There followed a lull in daytime bombing raids as the Allies attempted diplomatic maneuvers. Smaller formations of British night bombers continued to harry Sofia several times a week, largely unopposed as the Bulgarians air defenses lacked night-fighting capability.
American daylight raiders returned in a big way on March 30, 1944, when more than 450 B-17s and B-24s and British Halifiaxes, escorted by 150 P-38s, demolished the city center of Sofia. On that day, the Bulgarian pilots scored their greatest success ever, downing eight of the bombers and two Lightnings for no losses on their side.
This engagement uniquely involved four Czech-produced Avia B-135 fighters powered by 12Y engines similar to those on the D.520. The only 12 ever produced were mostly used as trainers by the RBAF, and their downing of a Liberator on March 30, 1944 was their sole combat engagement.
The Bulgarian fighter pilots’ luck turned decisively for the worse on March 30, 1944 as they intercepted another mega-raid of 350 B-24s and 100 P-51B Mustangs. The Bulgarians mistook the single-engine Mustangs for their own 109s — and were caught off their guard when the P-51s closed within short range and shot down nine Bulgarian fighters in one day for two losses.
The end was nigh in the air battle for Bulgaria, as the government’s dedication to the Axis cause began to waver and the Allies redirected their resources to new targets. Two Dewoitines scored the type’s last aerial victory — against a B-17 — on May 5, 1944. Devastating air strikes on June 12 and 28, 1944 wrecked Karlovo airfield, destroying 80 aircraft on the ground including many D.520s.
Two months later the Bulgarian government declared its neutrality — and was promptly overthrown by a pro-Soviet revolution.
The bombardment ultimately caused between one and two thousand deaths in Sofia and destroyed thousands of buildings. By the end of the bombing campaign, the city of 300,000 was largely depopulated, its inhabitants having fled to the countryside.
The bombardment arguably contributed to Bulgaria’s eventual defection from the Axis war effort, though to what extent is difficult to measure.The air attacks cost the Allied air forces 120 aircraft — around half due to accidents and other mishaps — and the lives of 256 flight crew, with hundreds more captured.
Bulgaria had managed to acquire decent combat aircraft and trained pilots through its alliance with Germany. Its fliers were relatively successful in consistently gnawing away at Allied bombing raids. This forced the U.S. Army Air Force to devote hundreds of escort fighters to protecting the bombers.
However, the little country lacked both the means and the political motives to sustain an aerial war of attrition with great powers, and in 1944 the Allied war machine could deploy additional warplanes faster than the Axis could shoot them down. New long-range escort fighters — notably the P-51 and P-47 — soon dramatically worsened the attrition of Axis fighters.
Dewoitine fighters are variously estimated to have shot down 11 to 14 Allied aircraft in the air war over Bulgaria. Once Bulgaria switched sides, the 6th Fighter Regiment was subordinated to the 288th Soviet Fighter Division, and Bulgarian Dewoitines began running interdiction, reconnaissance and ground-attack missions targeting German forces in Serbia and Macedonia.
Of the dozens of Bulgarian D.520s then still in service, between 7 and 11 more were lost in combat operations supporting the Allies. D.520s even reportedly tangled inconclusively on a couple occasions with superior German Fock-Wulf 190 fighters. The French fighters served briefly as trainers after the war before being retired in 1947.