The government of the Kingdom of Bulgaria under Prime Minister Georgi Kyoseivanov declared a position of neutrality upon the outbreak of World War II.
Bulgaria was determined to observe it until the end of the war; but it hoped for bloodless territorial gains in order to recover the territories lost in the Second Balkan War and World War I, as well as gain other lands with a significant Bulgarian population occupied by neighboring countries.
However, it was clear that the central geopolitical position of Bulgaria in the Balkans would inevitably lead to strong external pressure by both World War II factions.
On 15 February 1940, following the resignation of Georgi Kyoseivanov, Bogdan Filov was appointed Prime Minister of the Kingdom of Bulgaria.
On 7 September 1940, Bulgaria succeeded in negotiating the recovery of Southern Dobruja in the Axis-sponsored Treaty of Craiova.

On 1 March 1941, Bulgaria formally signed the Tripartite Pact, becoming an ally of Nazi Germany, the Empire of Japan, and the Kingdom of Italy.
German troops entered the country in preparation for the German invasions of the Kingdom of Greece and the Kingdom of Yugoslavia.
When Yugoslavia and Greece were defeated, Bulgaria was allowed to occupy all of Greek Thrace and most of Macedonia.
Bulgaria declared war on Britain and the United States, but resisted German pressure to declare war on the Soviet Union, fearful of pro-Russian sentiment in the country.

In August 1943 Tsar Boris died suddenly after returning from Germany (possibly assassinated, although this has never been proved) and was succeeded by his six-year-old son Simeon II.
Power was held by a council of regents headed by the young Tsar's uncle, Prince Kirill.
The new Prime Minister, Dobri Bozhilov, was in most respects a German puppet.

Resistance to the Germans and the Bulgarian regime was widespread by 1943, co-ordinated mainly by the Communists.
Together with the Agrarians, now led by Nikola Petkov, the Social Democrats and even with many army officers they founded the Fatherland Front.
Partisans operated in the mountainous west and south.
By 1944 it was obvious that Germany was losing the war and the regime began to look for a way out.
Bozhilov resigned in May, and his successor Ivan Ivanov Bagryanov tried to arrange negotiations with the western Allies.

Meanwhile, the capital Sofia was bombed by Allied aircraft in late 1943 and early 1944, with raids on other major cities following later.
But it was the Soviet army which was rapidly advancing towards Bulgaria.
In August Bulgaria unilaterally announced its withdrawal from the war and asked the German troops to leave: Bulgarian troops were hastily withdrawn from Greece and Yugoslavia.
In September the Soviets crossed the northern border.
The government, desperate to avoid a Soviet occupation, declared war on Germany, but the Soviets could not be put off, and on September 8 they declared war on Bulgaria – which thus found itself for a few days at war with both Germany and the Soviet Union.
On September 16, the Soviet army entered Sofia.
The government of the Kingdom of Bulgaria under Prime Minister Georgi Kyoseivanov declared a position of neutrality upon the outbreak of World War II. Bulgaria was determined to observe it until the end of the war; but it hoped for bloodless territorial gains in order to recover the territories lost in the Second Balkan War and World War I, as well as gain other lands with a significant Bulgarian population occupied by neighboring countries. However, it was clear that the central geopolitical position of Bulgaria in the Balkans would inevitably lead to strong external pressure by both World War II factions. On 15 February 1940, following the resignation of Georgi Kyoseivanov, Bogdan Filov was appointed Prime Minister of the Kingdom of Bulgaria. On 7 September 1940, Bulgaria succeeded in negotiating the recovery of Southern Dobruja in the Axis-sponsored Treaty of Craiova.
On 1 March 1941, Bulgaria formally signed the Tripartite Pact, becoming an ally of Nazi Germany, the Empire of Japan, and the Kingdom of Italy. German troops entered the country in preparation for the German invasions of the Kingdom of Greece and the Kingdom of Yugoslavia. When Yugoslavia and Greece were defeated, Bulgaria was allowed to occupy all of Greek Thrace and most of Macedonia. Bulgaria declared war on Britain and the United States, but resisted German pressure to declare war on the Soviet Union, fearful of pro-Russian sentiment in the country.
In August 1943 Tsar Boris died suddenly after returning from Germany (possibly assassinated, although this has never been proved) and was succeeded by his six-year-old son Simeon II. Power was held by a council of regents headed by the young Tsar's uncle, Prince Kirill. The new Prime Minister, Dobri Bozhilov, was in most respects a German puppet.
Resistance to the Germans and the Bulgarian regime was widespread by 1943, co-ordinated mainly by the Communists. Together with the Agrarians, now led by Nikola Petkov, the Social Democrats and even with many army officers they founded the Fatherland Front. Partisans operated in the mountainous west and south. By 1944 it was obvious that Germany was losing the war and the regime began to look for a way out. Bozhilov resigned in May, and his successor Ivan Ivanov Bagryanov tried to arrange negotiations with the western Allies.
Meanwhile, the capital Sofia was bombed by Allied aircraft in late 1943 and early 1944, with raids on other major cities following later. But it was the Soviet army which was rapidly advancing towards Bulgaria. In August Bulgaria unilaterally announced its withdrawal from the war and asked the German troops to leave: Bulgarian troops were hastily withdrawn from Greece and Yugoslavia. In September the Soviets crossed the northern border. The government, desperate to avoid a Soviet occupation, declared war on Germany, but the Soviets could not be put off, and on September 8 they declared war on Bulgaria – which thus found itself for a few days at war with both Germany and the Soviet Union. On September 16, the Soviet army entered Sofia.
Kingdom of Bulgaria