On 1st March 1939, Adolf Hitler ordered Plan ‘Z’ to be instigated. Plan ‘Z’ was the name given to the planned re-equipment and expansion of the existing Kriegsmarine (German Navy). The fleet was meant to challenge the naval power of Britain, and was to be completed by 1948.The plan called for a fleet of ten battleships and four aircraft carriers which were intended to engage the Royal Navy in battle. This force would be supplemented with numerous long-range cruisers that would attack British shipping. A small force of U-boats was also to be included in this fleet.

On the 15th March 1939 the German Wehrmacht occupied Czechoslovakia. German annexation of Czechoslovakia’s northern and western border had begun in 1938. Adolf Hitler’s pretext for this action was the alleged privations suffered by the ethnic German population living in the region. Although the Czechs had warmly welcomed the Germans when they had previously entered the Sudetenland, they stood silently in despair when the Nazis entered Prague. Having annexed the Sudetenland, Hitler’s next ambition was the conquest of Czechoslovakia. As Czechoslovakia was a major manufacturer of machine-guns, tanks and artillery, Hitler recognised the importance of occupying Czechoslovakia. By his annexation, Germany had gained over 2,000 field guns, 464 tanks and 500 anti-aircraft artillery pieces. Together with 43,000 machine-guns, over 1,000,000 rifle and pistols and about a billion rounds of ammunition, Germany had sufficient weaponry to arm approximately half of the Wehrmacht.

On the 20th March 1939, Germany issued an oral ultimatum to Lithuania demanding that the Klaipeda Region be given up or the Wehrmacht would invade Lithuania. The Klaipeda Region had been detached from Germany at the end of the Great War. After years of rising tension between Germany and Lithuania, the demand was expected. The ultimatum was issued just five days after the Nazi occupation of Czechoslovakia. Of the four signatories of the 1924 Klaipeda Convention, which guaranteed Lithuanian protection, Britain and France followed a policy of appeasement, while Italy and Japan openly supported Germany. Lithuania was forced to accept the ultimatum on the 22nd March 1939. For Germany it was the last territorial acquisition before the Second World War and for Europe it was a further escalation in pre-war tensions.

Following Adolf Hitler’s demands to return the Free City of Danzig (Gdansk) region of Poland to Germany, negotiations began on the 21st March 1939. Poland refused to agree to the demands. Germany began to move troop concentrations along the Polish border. On the 31st March 1939 in response to Nazi Germany’s Danzig demands and defiance of the Munich Agreement together with the occupation of Czechoslovakia, Britain and France pledged their support to assure Poland of her independence. Britain and France were not ready for war, and they needed time to properly re-arm and were determined to gain that time at any price. However, Polish leaders were not aware that the guarantee would not give additional support in the form of immediate military assistance.

The German-Romanian Treaty was signed in Bucharest on the 23rd March 1939. The German and Romanian governments signed the treaty for the “Development of Economic Relations between the Two Countries”, establishing German control over most aspects of the Romanian economy. The treaty had the effect of forcing Romania to join the Axis Powers because it had become a “German dependency” state.

British Prime Minister Neville Chamberlain drafted the British guarantee of Poland’s independence on the 30th March 1939, after making it clear that an attack would not be tolerated. This guarantee was in response to Nazi Germany’s defiance of the Munich Agreement and the occupation of Czechoslovakia. On the 6th April 1939, during a visit to London by the Polish Foreign Minister, it was agreed to formalise the assurance as an Anglo-Polish military alliance. That assurance was extended on the 13th April 1939 to Greece and Romania following Italy’s invasion of Albania.

The Spanish Civil War ended when General Francisco Franco proclaimed victory in a radio speech on the 1st April 1939. The last of the Republican forces, made up of mainly relatively urban left wing leaning citizens and supported by anarchists and communists, were forced into unconditional surrender. Franco was the leader of the Nationalist Party, consisting largely of Catholic aristocratic citizens, who had led his nation through four years of civil war. After the end of the war, there were harsh reprisals against Franco’s former enemies. Thousands of Republicans were imprisoned and at least 30,000 executed. Many others were put to forced labour, building railways, draining swamps and digging canals.

On the 3rd April 1939, Germany started planning the invasion of Poland known as “Fall Weiss”. The German military High Command finalised its operational orders on the 15th June 1939 and the invasion commenced on the 1st September 1939, precipitating the Second World War.

The Italian invasion of Albania was a brief military campaign by the Kingdom of Italy against the Albanian Kingdom between the 7th to the 12th April 1939. Albania had long been of considerable strategic importance to Italy as it allowed the Italian navy to have control of the entrance to the Adriatic Sea. It also provided Italy with a beachhead in the Balkans. The conflict was a result of Italian dictator Benito Mussolini’s imperialistic policies. King Zog I was forced into exile when Albania was over-run and the country was made part of the Italian Empire.

American President Franklin D. Roosevelt wrote a letter Adolf Hitler on the 14th April 1939 with a request that a fear of a new world war conflict be averted by discussion and negotiation. He was aware that Hitler had repeatedly stated Germany had no desire for war, but Roosevelt required assurance that Germany would not attack or invade any other European nation. The United States would be willing to participate in an effort to bring world peace. Hitler’s reply on the 28th April 1939 that the Treaty of Versailles in 1919 heaped many injustices upon the German people. He pointed out that he had brought Germany into full employment by building a new infra-structure and restored some previously lost territories back to Germany. The reports that Germany intended to attack Poland, were a “mere invention by the international press”, which had led Poland to make an agreement with England. Hitler considered this to be a breaking of the Polish-German non-aggression pact, which was signed in 1934, was therefore no longer in existence. Hitler had not really answered Roosevelt’s question of whether he had finished with aggression and would he carry out his plan to attack Poland.

On the 18th April 1939, Russia’s President Joseph Stalin proposed an anti-Nazi alliance with Britain and France. Such an agreement could have changed the course of 20th century history. Stalin proposed moving a million Russian troops complete with supplies and weapons to the German border providing Polish objections be overcome to allow the Red Army crossing its territory. Britain and France would only enter into negotiations but were not authorised to commit to binding deals. However, on the 21st August 1939 the French made a desperate attempt to revive the talks but they were rebuffed as secret Soviet-Nazi talks were well advanced.

On the 26th April 1939, Britain reintroduced conscription. At long last, the British policy of appeasement was being abandoned. Despite this, Hitler firmly believed that there would be no retaliation from Britain and France if he attacked Poland.

On the 28th April 1939, Adolf Hitler denounced the Anglo-German Naval Agreement which had been signed in 1935. His excuse was that the British “guarantee” of Polish independence was part of the encirclement policy of Germany and to prevent the emergence of a new naval treaty. The Germans began refusing to share information about their shipbuilding which they considered to be justification of Hitler’s ordering the implication of Plan Z on the 1st March 1939.

The Battles of Khalkhyn Hol were a series of engagements beginning on the 11th May 1939 and lasted until the 16th September 1939. The battles were fought along the Soviet-Japanese border with the participants being the Soviet Union, Mongolia, Japan and Manchukuo. Mongolia was a communist state allied with the Soviet Union, and Manchukuo was a puppet state of Japan. There was dispute about the border between Manchukuo and Mongolia called the Khalkhyn Hol which resulted in skirmishes between the two sides. By the 31st August 1939, Japanese forces were nearly totally destroyed after having the Soviet army completely encircling them. The Soviet Union and Japan agreed to a cease-fire which was effective on the 16th September 1939 allowing Russia to proceed with the invasion of Poland on the 17th September 1939.

On the 22nd May 1939, Fascist Italy and Nazi Germany signed a military and political alliance known as the “Pact of Steel”. Originally the pact drafted a three way military alliance between Japan, Italy and Germany. While Japan wanted the pact to be aimed at the Soviet Union, Italy and Germany wanted it aimed at the British Empire and France. The pact was signed without Japan due to this disagreement. With Italy’s resources stretched to capacity, many Italians believed Italy’s alliance with Germany would provide time to regroup. Influenced by Adolf Hitler, discrimination policies against the Jews in Italy was instituted by Benito Mussolini.

The Focke Wulf Fw 190 made its first flight on the 1st June 1939, which alongside the Messerschmitt Bf 109 became the backbone of Luftwaffe’s Jagdwaffe (Fighter Force). The Fw 190 was a German was a single seater, single engine fighter aircraft which was widely used in the Second World War. It had a twin-row fourteen cylinder radial engine which enabled it to lift larger loads allowing it to also be used as a day fighter, ground attack aircraft, fighter-bomber and occasionally night-fighter. The Fw 190 began operational flying over France in August 1941, and it soon became apparent that it proved to be superior to the RAF Spitfire. The ability to out-turn the Fw 190 was the Spitfire’s only advantage, with the German fighter having greater firepower and superior manoeuvrability especially at low to medium altitude.

The Tientsin Incident began on the 14th June 1939 when the Japanese blockaded the British concession in Tientsin, China (modern day Tianjin). The British Royal Navy and the British Foreign Office reported on the 26th June 1939 the only way to break the Japanese blockade was by deploying warships to the area. However, given the current tensions with Germany, such a deployment would not be advisable. To appease the Japanese, on the 20th August 1939 despite protest from the Chinese government, the British handed over four Chinese nationals to the Japanese. The four men had been accused of killing a pro-Japanese Chinese collaborationist and were eventually executed by the Japanese. The Tientsin Incident marked the beginning of a pattern in which Japan would seek confrontation with Western powers backing the Chinese. This practise would ultimately end with Japan going to war with the United States of America and Britain in December 1941.

On the 17th June 1939, the Norwegian, Swedish and Finnish governments rejected an offer from the German government to negotiate a mutual non-aggression pact. The German offer was spurred by U.S. President Franklin Roosevelt’s suggestion that Germany’s neighbours felt threatened by aggression. These states also announced their opposition to a joint Anglo-French-Soviet guarantee of the independence of the Baltic States. The Nordic foreign ministers discussed the German offer at length, but agreed to remain aloof from all commitments to rival power groups. Relations between the Finns and the Soviets began to cool, especially as the Soviet delegation to the League of Nations blocked League approval for the fortifications of the Aaland Islands. The Danish government was the only Scandinavian power to accept the German offer.

The Einstein-Szilard letter was a letter written by Leó Szilárd and signed by Albert Einstein that was sent to the United States President Franklin D. Roosevelt on the 2nd August 1939. Szilárd was a Hungarian physicist, who was living in the United States at the time, had been a student of Einstein, a German-Jewish physicist who had immigrated to America when Adolf Hitler came to power. The letter warned that Germany might develop atomic bombs and suggested that the United States should start its own nuclear programme. Roosevelt took heed of the advice and prompted the action which eventually resulted in the Manhattan Project developing the first atomic bomb. The discovery of uranium fission in December 1938 was reported in the 6th January 1939 issue of Die Naturwissenschaften. Lise Meitner, a Jewish Austrian-Swedish physicist, correctly identified the process as nuclear fission which was reported on the 11th February 1939 issue of Nature.

The Molotov-Ribbentrop Pact was a neutrality pact between Nazi Germany and the Soviet Union which was signed in Moscow on the 23rd August 1939. The signatories were foreign ministers Joachim von Ribbentrop of Germany and Vyacheslav Molotov of the Soviet Union. The pact provided a written guarantee of non-belligerence by each party to the other and a secret protocol that divided the territories of Poland, Lithuania, Latvia, Estonia, Finland and Romania into German and Soviet hands. They both anticipated “territorial and political rearrangement” of these countries. The Soviet Union had wanted good relations with Germany for years and was pleased to see that Germany embraced the same ideas.

The Germans, prompted by the British, issued one last diplomatic ultimatum to Poland on the 30th August 1939 stating they were willing to commence negotiations about the Polish Corridor. This was not in Hitler’s previous demands which was only for the restoration of Danzig. The ultimatum was that a Polish representative with the power to sign an agreement had to arrive in Berlin the following day. In the meantime Germany would draw up a set of proposals for consideration. On the night of the 30/31st August 1939 the German Foreign Minister Joachim von Ribbentrop read the proposals to the British Ambassador, who requested a copy for the transmission to the Polish government. Ribbentrop refused the request on the grounds that the Polish representative had failed to arrive by midnight Ribbentrop interpreted this as bring Poland had rejected Germany’s offer and negotiations with Poland came to an end.

On the 31st August 1939, Hitler signed the order for an assault on Poland. The Germans staged a phony raid on a German radio station at Gleiwitz and were able to blame the Polish for the “unprovoked attack”, giving the Germans the excuse they needed to invade Poland.

Without declaring war, Germany invaded Poland on the 1st September 1939. The co-ordinated air and land attack was conducted with such brutal efficiency that “blitzkrieg” became a feared offensive tactic. The inter-war period ended with the invasion which initiated the start of the Second World War.