Its possible to describe the Second World War as a war with a primary cause and several secondary causes or a war of multiple causes.

Political factors - War is essential for the survival of totalitarian regimes…

September 1st 1939 - POLAND: German air assault against Polish airfields, army bases and railroads. Disrupted the Polish troops. The air attack was followed by the advance of infantry and armored divisions - some of them reached fifty miles into Poland within 48 hours - BLITZKRIEG. The Polish army was numerically superior (over 2 million men) but lacked modern equipment and methods of transport… On the 10th of September the Polish High Command ordered a general retreat towards the South-east (the border towards Rumania). This retreat was efficient when the USSR attacked Poland on the 17th of September. Peace negotiations started on the 28th of September. On the 5th of October Poland gave up. There was no direct assistance from Poland’s allies Britain and France. Poland was divided in 3 parts; the eastern part became Russian, the western part became German and the ”middle” (called Government General) was under German control.
Stalin and the Soviet Union had little faith in Hitler’s promises and therefore they wanted to build a buffer zone between them and the enlarged Germany. To this end a series of treaties were made with the Baltic states; Estonia, Latvia and Lithuania. They agreed to allow Russian troops and ships to be stationed in their countries. Finland refused!

November 28th 1939 - FINLAND: Finland was attacked and two days later USSR declared war against Finland. The Finnish Winter War had begun. Finland appealed to the League of Nations and they asked for assistance from the Western world. Sweden and Norway sent some volunteers. France and Britain prepared an expeditionary force that officially should aid Finland. They wanted to travel through northern Norway and Sweden - and capture the Swedish ore mines (which stood for 51% of Germanys supplies…). This force was ready to sail when Finland decided to surrender in March 1940. Finland lost land in the peace treaty. Once again Britain and France decided to not be involved in the actual war. That’s why some American journalists christened the war ”the Phoney War”.

BRITAIN & FRANCE: prepared for the type of war they expected to come;

In France the French Commander-in-Chief in the north General Gamelin decided that he did not have sufficient forces to launch a major assault on the German "SIEGFRIED LINE” so he stopped in front of it! When the assault of Poland was over the French felt increasingly vulnerable - so most of them secretly withdrawd to the ”MAGINOT LINE”. Then they sat down and waited…

The Northern part of the Maginot Line 1940

April 9th 1940 - DENMARK & NORWAY: On the 9th of April 1940 Denmark allowed German troops to occupy the country. Two days before - April 7th - German ships were seen to be moving northwards. France and Britain started to mine Norwegian coastal waters. On April 9th German troops landed in the five main ports and cities of Norway: Oslo, Bergen, Trondheim, Stavanger and Narvik. The Norwegian resistance was greater than expected - two German cruisers were damaged. In the north (Narvik) the resistance was successful for some time (with the aid of British, French and Polish troops). In early June they withdrew. King Haakon VII and his government managed to escape to London. Norway was now in German hands.

The defeat of Poland, Finland and Norway led to a government change in both Britain and France! Public opinion and the elected representatives expressed their discontent at the lack of allied support for especially Finland and Norway:

In France, the Soviet victory in Finland, led to the downfall of DALADIER. He was replaced by RAUL REYNAUD on March 20th 1940.

Both these new governments were broad coalitions which included both conservatives and socialists.

May 10th 1940 LUXEMBOURG, HOLLAND & BELGIUM: Germany attacked Luxembourg, Holland and Belgium the 10th of May 1940. Luxembourg fell at once but Holland and Belgium expected an attack and they were prepared. They thought they would defend themselves along the rivers and waterways - but their armies were small and they lacked artillery and air support. Germany broke the Dutch defensive system within 3 days. On the 14th of May Rotterdam was systematically bombed (part of the city was destroyed). Cease fire came the same evening. Queen Juliana and her family fled to Britain and Holland surrendered. The allies had more hope of defending Belgium. The defense line went from the MAGINOT LINE along SEDAN to NAMUR and then along the river DYLE. Belgian troops were supposed to hold the northern part, British in the centre and French in the south. The Germans attacked the weakest point in the south through the ARDENNES. They met very little resistance and where soon on the south and west side of SEDAN. The allied could not agree on how and where to counterattack. Meanwhile a retreat of their troops towards the English Cannel continued. On the 27th of May 1940 King Leopold III surrendered Belgium to the Germans. The allied decided to try to get out by the Channel in NIEUPORT and DUNKIRK. The ”Miracle of DUNKIRK” - over 300.000 men were rescued by 222 naval ships and over 650 smaller private boats!

June 5th 1940 FRANCE: Germany attacked northern France the 5th of June 1940 (called Fall Rot – Case Red). Numerous French divisions were cut off and in retreat. Millions of French refugees were now making their way towards the south. German forces outflanked the Maginot Line to attack the larger territory of France. Italy declared war on France on 10 June. The French government fled to Bordeaux, and Paris was occupied on 14 June. The French government sent out an appeal for armistice. As Compiègne had been the site of the 1918 Armistice, which had ended World War I with a humiliating defeat for Germany, Hitler viewed the choice of location as a supreme moment of revenge for Germany over France. The armistice was signed on 22 June in the very same railway carriage in which the 1918 Armistice was signed (removed from a museum building and placed on the precise spot where it was located in 1918). Hitler sat in the same chair in which Marshal Ferdinand Foch had sat when he faced the defeated German representatives. The French Second Army Group, under the command of General Pretelat, surrendered the same day as the armistice and the cease-fire went into effect on 25 June 1940 (the Second Armistice at Compiègne).
France was divided into a German occupation zone in the north and west, a small Italian occupation zone in the southeast and a nominally independent state in the south, to be based in the spa town of Vichy, dubbed Vichy France. The new French state, headed by Marshal Pétain (French WWI hero), accepted its status as a defeated nation and attempted to buy favor with the Germans through accommodation and passivity. Charles de Gaulle, who had been made an Undersecretary of National Defense by Reynaud, in London at the time of the surrender, made his Appeal of 18 June. In this broadcast he refused to recognize the Vichy government as legitimate and began the task of organizing the Free French forces. Numerous French colonies abroad (French Guiana, French Equatorial Africa) joined de Gaulle rather than the Vichy government. The British began to doubt Admiral Darlan's promise to Churchill not to allow the French fleet at Toulon to fall into German hands by the wording of the armistice conditions; they therefore attacked French naval forces in Africa and Europe, which led to feelings of animosity and mistrust between the former French and British allies. After growing resistance within occupied France Vichy France was occupied on 10 November 1942 and all of France remained under German occupation until after the Allied landings in 1944.