In World War II, as in the First World War, the Kingdom of Bulgaria was an ally of Germany. Therefore, the often-held statements that Bulgarians and Russians in the twentieth century have never fought among themselves are completely untrue. During the First World War, in 1916-1917, Russian and Bulgarian units repeatedly had fighting clashes on the Romanian and Thessaloniki fronts, sometimes very fierce. For example, in the city of Monastir in Macedonia in November 1916, the 2nd Special Russian Brigade lost about a third of its personnel in battles with Bulgarian troops. In Russia, by the end of 1917, there were about 2000 (according to other sources - 5,000) prisoners of war of the Bulgarian army.
In March 1941, Bulgaria joined the Tripartite Pact and granted Germany its territory to accommodate troops preparing for an invasion of Greece. In April 1941, German military operations spread to Yugoslavia. Bulgaria did not formally declare war on Greece and Yugoslavia, but took part in their occupation, annexing significant territories (after the war all of them were returned). Bulgaria also refrained from declaring war to the Soviet Union after June 22, 1941. Traditionally this is due to fear of the ruling circles of Bulgaria that its army will fight against the Russians, to which the country owes its liberation from the Turkish yoke. However, in the First World War this circumstance did not prevent the Bulgarians from fighting against the Russian Empire. Now Russia was ruled by the Bolsheviks, to whom the Bulgarians could not feel any gratitude. The real reason, apparently, was the fear of sending troops in general anywhere. The fact is that the monarchical regime in Bulgaria experienced a constant internal political crisis. However, on December 13, 1941, under the pressure of Hitler, Bulgaria still declared war to the Western allies of the USSR, the USA and Great Britain, far from it.
It is also false that there were no fighting clashes between the Soviet and Bulgarian armed forces in World War II. Formally not fighting against the USSR, the Bulgarian military were part of the convoys of German and Romanian transports in the Black Sea. For their part, the submarines of the Soviet Black Sea Fleet were active near the coast of Bulgaria. They put mines on the Bulgarian ports of Varna and Burgas, conducted reconnaissance, and, on occasion, attacked convoys. Already in 1941 there were a number of clashes in which the Bulgarian fleet and aviation took part. So, before the end of the year, the Bulgarian coast guard aircraft attacked the Soviet submarines five times, but only once hit the target, and the fact of sinking is in question. It is well known that two Soviet submarines were blown up in Bulgarian territorial waters on mines. And on December 6, 1941 in the Burgas area Bulgarian patrol boats disabled the Soviet submarine Shch-204. The Bulgarian transport "Shipka" was blown up on Soviet mines. September 9, 1941 Soviet submarine L-4 in the surface position fired from the guns and sank the Bulgarian ship "Success". Clashes arose later, but less frequently, since, while the Crimea was under the control of the Axis countries (from July 1942 to May 1944), Soviet submarines found it difficult to reach the coast of Bulgaria.
Another misconception about Bulgaria during the Second World War is that it was occupied by Germany. German troops twice in 1941-1944. entered the territory of Bulgaria. The first time it was done for a military operation against Greece and Yugoslavia and with the consent of the Bulgarian government. Upon its completion, the German units left Bulgaria. During the war with the USSR, German, Italian and Romanian vessels used the repair capabilities of the Bulgarian naval bases in Varna and Burgas. However, in early 1944, at the request of the Soviet Union, the Bulgarian government closed their access to the Bulgarian ports. Under the influence of the victories of the anti-Hitler coalition, the political crisis in Bulgaria intensified. The clandestine struggle waged against the authorities by the communists in union with other leftist parties was widening. At the end of August 1944, the German front collapsed near Iasi and Romania withdrew from the war with the USSR. The German units used the territory of Bulgaria for retreat, and the Bulgarian troops did not impede their movement. This was the second invasion of the Germans by the Bulgarian land, which was already forcible, but aimed not at occupation, but as a retreat to the territory of Yugoslavia. On August 26, the Bulgarian government officially announced the internment and disarmament of the German units in the country, but in fact it sought to avoid a military clash both with the retreating Germans and with the Red Army.
The Soviet leadership regarded this as a manifestation of disloyalty and on September 5 declared war on Bulgaria. According to the Soviet command, at that time in Bulgaria there were about 30 thousand German soldiers. On September 2, a plan was drawn up to seize the Bulgarian ports. On the night of 7 to 8 September, the ships and aircraft of the Black Sea Fleet began landing. At that time, there were no more German ships or German troops: on 26-30 August, the Germans flooded 74 units of the fleet on the roads of Varna and Burgas. On the morning of September 8, Soviet troops of the 3rd Ukrainian Front, under the command of Army General F.I. Tolbukhin crossed the border of Bulgaria from Romania. On the night of September 5, the Bulgarian government decided to declare war on Germany, but at the insistence of the War Minister IK. Marinova put off this note for three days. During these three days, Bulgaria declared war on the part of the USSR, and the organization of the anti-government uprising in Sofia was optimized. As it turned out later, Marinov was already conducting negotiations with the Communists, ensuring his preservation of his post under the new regime. When in the evening of September 7 it became known that Bulgaria and Germany were at war, the first was in a unique position of the country, formally fighting along with both coalitions! But it did not last long. Already on the night of September 9, a coup took place in the capital, and the power passed to the government of the Fatherland Front, in which the leading role was played by the Communists. In September 1944, in the territory of Bulgaria, the Soviet troops lost 977 servicemen, including those who died in battle, as well as those who died from wounds and illnesses.