On December 13, 1941, Bulgaria declared war on the USA and Great Britain. This was required by our allied obligations to the Third Reich.
On June 5, 1942, the USA, in turn, also declared war on the Kingdom of Bulgaria. On June 12, 1942, 13 long-range B-24 Liberator heavy bombers, based at Fayd Airport on the Suez Canal, flew over the Mediterranean Sea, Turkey and the Black Sea, passed over land in the area of Constanța and bombed the oil region of Ploiești. Damage to the refineries was minor. The air defense and fighter aircraft of the Luftwaffe and the Romanian Air Force did not react. This was the first strike by American strategic aviation deep into the continent.
In the autumn of 1943, as a result of the successful Allied landing in Sicily, the territory of southern Italy brought the Balkans within the reach of Allied aviation. The bombing of Bulgaria began, lasting from October 20, 1943 to September 17, 1944.
Cities in the annexed parts of Yugoslavia were also bombed, after prior coordination with Tito.