On March 1, 1941, Bulgaria joined the Axis by signing the Tripartite Pact. Germany had long pressured Bulgaria into allying with the Axis, but the Bulgarian government balked at getting involved in the war. However, with the Italian offensive into Greece being turned back, Adolf Hitler decided to intervene, and demanded the passage of German forces into Bulgaria for the invasion of Greece (and later including Yugoslavia). Recognizing futility to stop a German attack into its territory, the Bulgarian government acquiesced, and joined the Tripartite Pact with assurances of being given Greek territory and continued diplomatic relations with its neighbors Turkey and the Soviet Union. At that time, Germany and the Soviet Union had a ten-year non-aggression pact.
(Taken from The Balkan Campaign – Wars of the 20th Century – World War II in Europe)
In August 1940, Hitler gave secret instructions to his military high command to prepare a plan for the invasion of the Soviet Union, to be launched in the spring of 1941. In October 1940-January 1941, the Germans launched fierce air attacks on Britain, which failed to force the latter to capitulate as Hitler had hoped. Hitler then suspended his planned invasion of Britain and instead focused on other ways to bring it to its knees. He turned to the Mediterranean Sea, whose control by Germany and Italy would have the effect of cutting off Britain from its colonies in Africa and Asia via the Suez Canal. In this plan, German forces would capture Gibraltar through Spain, thus sealing off the western end of the Mediterranean Sea, while the Italian Army in Libya would capture British-controlled Egypt as well as the Suez Canal, sealing off the eastern end of the Mediterranean Sea. German forces would join in the final stages of the Italian offensive.
As the German military formulated the invasion plan of the Soviet Union and the means to knock Britain out of the war, Hitler was determined that no complications arose that would interfere with these objectives. Foremost, Hitler had no appetite for turmoil to break out in southeastern Europe, especially the highly volatile Balkan region, the “powder keg” that had sparked World War I. Politically and strategically, Hitler wanted stability in the Balkans to keep away the Soviet Union, with whom Germany had a tenuous non-aggression pact. Conflict in the Balkans would most likely prompt intervention by Russia, which traditionally held a strong influence there.
Hitler had long stated that he had no territorial ambitions on the Balkans. Instead, Germany’s main interest there was purely economic, as the Balkan countries were Germany’s biggest partners, supplying the latter with food and mineral resources. But of the greatest importance to Hitler were the Ploiesti oil fields in Romania, which provided the German military and industry with vital petroleum products.
Germany and Italy mediated two territorial disputes involving Romania and its neighbors: on August 21, 1940, Romania was persuaded to cede Southern Dobruja to Bulgaria, and on August 30, 1940, it also relinquished one-third of Transylvania to Hungary. A few weeks earlier, in late June-early July 1940, Soviet leader Joseph Stalin had used strong-arm tactics to force Romania to cede its northeastern regions of Bessarabia and Northern Bukovina to the Soviet Union.
Meanwhile, Hitler strove to convince Mussolini to stall the latter’s territorial ambitions in the Balkans. Mussolini had long viewed that in the German-Italian partition of Europe, southeastern Europe and the Balkans fell inside the Italian sphere of control. Italian forces had invaded Albania in April 1939 (separate article), and after the fall of France in June 1940, Mussolini exerted pressure on Greece and Yugoslavia, and threatened them with invasion. At that time, Hitler was able to convince Mussolini to suspend temporarily his Balkan ambitions and instead focus Italian efforts on defeating the British in North Africa.
But on October 7, 1940, at the request of Romanian dictator Ion Antonescu, German forces entered Romania to guard against a Soviet invasion; for Hitler, it was to protect the vital Ploiesti oil fields. Mussolini was outraged by this German action, as he believed that Romania fell inside his zone of control. Also for Mussolini, Hitler’s move into Romania was only the latest in a long list of stunts that had been made without previously consulting him, and one that had to be reciprocated, or as Mussolini put it, “to repay him [Hitler] with his own coin”. Hitler had invaded Poland, Denmark, Norway, France, and the Low Countries without informing Mussolini beforehand.
On October 28, 1940, Mussolini, without notifying Hitler, launched the invasion of Greece (previous article), despite insufficient military preparation and against the counsel of his top generals. The operation was a disaster, as the motivated Greek Army threw back the Italians to Albania, and then launched its own offensive. Within three months, the Greeks occupied a quarter of Albanian territory. Greece had declared its neutrality at the start of World War II. But because of the Italian invasion, the Greek government turned to Britain for assistance. In early November 1940, British forces had arrived, and occupied two strategically important Greek islands, Crete and Limnos.
The unexpected Italian attack on Greece and likelihood of British intervention in the Balkans shocked Hitler, seeing that his efforts to try and maintain peace in the region had failed. His prized Ploesti oil fields and the whole southeastern Europe were now vulnerable. On November 4, 1940, Hitler decided to become involved in Greece in order to bail out his beleaguered ally Mussolini and to forestall the British. On November 12, 1940, the German High Command issued Directive No. 18, which laid out the German plan to contain the British in the Mediterranean: German forces would invade northern Greece and Gibraltar in January 1941, and then assist the Italians in attacking Egypt in the fall of 1941. However, Spain’s pro-Axis dictator General Francisco Franco refused to allow German troops into Spain, forcing Germany to suspend its invasion of Gibraltar. On December 13, 1940, the German military issued Directive No. 20, which finalized the invasion of Greece under codename Operation Marita. In the final plan, German forces in Bulgaria would open a second front in northeastern Greece and capture the whole Greek northern coast, link up with the Italians in the northwest, and if necessary, push south toward Athens and seize the rest of Greece. Operation Marita was scheduled for March 1941; however, delays would cause the invasion to be launched one month later.
For the invasion of Greece, Hitler considered it necessary to bring into the Axis fold the governments of Hungary, Romania, Bulgaria, and Yugoslavia, notwithstanding their stated neutrality at the start of the World War II. With their cooperation, German forces would cross their territories through Central and Eastern Europe, as well as control their military-important infrastructures, such as airfields and communications systems. Hungary, which had benefited territorially in the German seizure of Czechoslovakia and Axis arbitration of Transylvania, was drawn naturally to Germany. On November 20, 1940, the Hungarian government joined the Tripartite Pact . Three days later, Romania also joined the Pact, as Romanian leader Antonescu was motivated to do so by fear of a Soviet invasion. In succeeding months, large numbers of German forces and weapons, passing through Hungary, would assemble in Romania, mainly for the planned invasion of the Soviet Union (whose operational plan would be finalized in December 1940 under the top-secret Operation Barbarossa).
Bulgaria balked at joining the Pact and thus be openly associated with the Axis, and also was concerned that participating in the invasion of Greece would leave its eastern border vulnerable to an attack by Turkey, which was allied with Greece. The Bulgarians also were aware of a Soviet plan to capture Varna, Bulgaria’s Black sea port, which the Soviets would use to seize control of the Turkish Straits, which was a source of a long-standing dispute between the Soviet Union and Turkey.
However, Hitler exerted strong diplomatic pressure on Bulgaria and also promised to protect Bulgarian territorial integrity. Bulgaria acquiesced and agreed to allow German troops to enter Bulgarian territory. On February 28, 1941, German engineering crews bridged the Danube River at the Romanian-Bulgarian border, and the first German units crossed into Bulgaria and continued to that country’s eastern border. The next day, March 1st, Bulgaria joined the Tripartite Pact, officially joining the Axis. On March 2, 1941, German forces involved in Operation Marita entered Bulgaria and proceeded south to the Bulgarian-Greek border.
To assure Turkey of German intentions, Hitler wrote to the Turkish government to explain that the German presence in Bulgaria was directed at Greece. To further allay the Turks, German troops were positioned far from the Turkish border. The Turkish government accepted the German clarification, and agreed to stand down its forces during the German attack on Greece.
Meanwhile, Greece was aware of German plans, and in the previous months, held talks with Britain and Yugoslavia to formulate a common strategy against the anticipated German attack. The dilemma for Greece was that by March 1941, the greater part of its military forces were still tied down against the Italians in southern Albania, leaving insufficient units to defend the rest of the country’s northern border. At the request of the Greek government, Britain and its dominions, Australia and New Zealand, sent 58,000 troops to Greece; this force arrived in March 1941 and deployed in Greece’s north central border.
With regards to Yugoslavia, Hitler exerted great effort to try and persuade the officially neutral but Allied-leaning government of Yugoslav Prime Minister Dragisha Cvetkovic to join the Axis. In a series of high-level meetings between the two countries which even included Hitler’s participation, the Germans offered sizable rewards to Yugoslavia for joining the Axis, including Greek territory that would include Salonica which would give Yugoslavia access to the Aegean Sea. Talks went nowhere until Hitler met with Prince Paul on March 4, 1941, which led two weeks later to the Yugoslav government agreeing to join the Axis. On March 25, 1941, Yugoslavia signed the Tripartite Pact, motivated by a secret clause in the agreement that contained three stipulations: the Axis promised to respect Yugoslavian sovereignty and territorial integrity, the Yugoslavian military would not be required to assist the Axis, and Yugoslavia would not be required to allow Axis forces to pass through its territory. But two days later, March 27, the pro-Allied Serbian military high command deposed the Yugoslav government and installed itself in a military regime, arrested Prince Paul, and named the 17-year old minor crown prince as King Peter II. The new military government assured Germany that Yugoslavia wanted to maintain friendly ties between the two countries, albeit that it would not ratify the Tripartite Pact. Anti-German mass demonstrations broke out in Belgrade and other Serbian cities.
As a result of the coup, a furious and humiliated Hitler believed that Yugoslavia had taken a stand favoring the Allies, despite the new Yugoslav government’s conciliatory position toward Germany. On March 27, 1941, just hours after the coup, Hitler convened the German military high command and stated his intention to “destroy Yugoslavia as a military power and sovereign state”. He ordered the formulation of an invasion plan for Yugoslavia, which was to be carried out together with the attack on Greece. Despite the time constraint (the attack on Greece was set to be launched in ten days, April 6, 1941), the German military finalized a lightning attack for Yugoslavia, code-named Operation 25, to be under taken in coordination with the operation on Greece.
Hitler invited Bulgaria to participate in the attack on Yugoslavia, but the Bulgarian government declined, citing the need to defend its borders. As well, Hungary demurred, as it had just recently signed a non-aggression pact with Yugoslavia, but it agreed to allow the German invasion forces to mass in its southwestern border with Yugoslavia. Romania was not asked to join the invasion.
Mussolini, after conferring with Hitler, agreed to participate, and the Italian forces were to undertake the following: temporarily cease operations at the Albanian front; protect the flank of the German forces invading from Austria to Slovenia; seize Yugoslav territories along the Adriatic coast; and link up with German forces for the invasion of Greece.
On April 3, 1941, Yugoslavia sent emissaries to Moscow to try and arrange a mutual defense treaty with the Soviet Union. Instead, on April 5, the Soviet government agreed only to a treaty of friendship and non-aggression with Yugoslavia, which did not promise Soviet protection in case of foreign aggression. As a result, Hitler was free to invade Yugoslavia without fear of Soviet intervention. On April 6, 1941, Germany and Italy launched the invasions of Yugoslavia and Greece, discussed separately in the next two chapters.