More than 70 years ago, 6th Fighter Regiment from the Bulgarian His Majesties Air Force started reequipment with French fighters Dewoitine D.520. In the cockpits of these war planes Bulgarian pilots accepted the unequal battle for the sovereignty of the national sky against the Anglo-American bombardments in 1943-1944. They continued the use of Dewoitines in air interdiction and recce missions against the Germans, supporting Bulgarian Army offensive operations in the Western Balkans.