The campaign in Western Europe
The French and British armies did not take advantage of the German attack on Poland, which left the western front of Germany exposed and with the German Army lacking the necessary forces to attack France. Instead, the British and French armies carried out a number of hesitant actions, such as occupying several villages and advancing a few kilometers. Instead of bombs, the Allies dropped leaflets on Germany. In general, it can be said that at this stage (between September 1939 and May 1940) there was no actual war on the German-French border. This phase of the war was called "The Phony War."
The German invasion plan of 1940 (Sichelschnitt) was designed to deal with the problem of the fortified line by bypassing it. A diversionary force operated against the fortified line whilst the main force made a surprise breach of the exposed French wing through the Ardennes forests rapidly overcoming the obstacles of nature and the difficult terrain. Thus the Germans avoided the need to make a frontal attack on the Maginot line. The attack began on May 10 and the German forces penetrated quickly through Belgium and deep into France. At the same time, another German force conquered Holland, causing many casualties amongst the citizens and the brave Dutch army, which had no chance of stopping the invaders who outnumbered them vastly, although fighting bravely. The German offensive in France lasted until May 24, and was stopped because of Hitler's personal command when the German troops reached the shores of the Channel near the town of Dunkirk.
By the beginning of June German forces had occupied the entire northern part of France, which was to have been protected by the Maginot Line.
British troops in France who fought alongside the French numbered more than 400,000. Thanks to the surprising halt of the German offensive, some 340,000 soldiers, most of them British, but also many French soldiers and others, were evacuated from the shores of Dunkirk in a magnificent operation. The mission was carried out by a miscellaneous fleet of ships, including ships of the navy, hundreds of civilian yachts, fishing boats and British vessels of every type in what was called "Operation Dynamo". Most of the ships sailed back and forth to Dunkirk several times in the same operation that began on 27 May and ended on 4 June 1940.
The heavy equipment and even much of the personal weapons of the soldiers who had been evacuated from Dunkirk were left behind on the shore, but the return of most of the trained soldiers to England provided a basis for building the necessary forces for the protection of the England against the danger of an immediate German invasion and later for returning as victors to the Continent of Europe in June 1944. The evacuation of the Allied forces from Dunkirk was carried out under incessant attacks by the German air force and artillery, and the waging of bitter and continuous air battles between British and German planes, was considered the first "success" of Allied forces in the war so far. This is despite the fact that, as Churchill said in his report to the House of Representatives, success of this kind does not replace victory in battle or "war is not won by evacuations and retreats". This was also the first, but not the last time that Hitler intervened personally in the conduct of the war to the detriment of the Army's operations. At the beginning of June the fighting continued in central France and Paris was occupied in less than a week. France surrendered on June 14, despite fierce opposition by the French army toward the end. For lack of any alternative, the French government made approaches for a cease-fire that led to the signing of an agreement with Germany on 22 June 1940 according to which North and West France were to come under German occupation. The South of France was not occupied and a collaborationist French Government was set up in Vichy (hence the name "Vichy Regime") leadership of the aged Marshal Petain the, the hero of the First World War. Petain replaced the belligerent Prime Minister Paul Reynaud, who resigned because he did not want to be the person who approved in the name of France, the surrender to the Germans.
The French and British armies (together with the armies of Belgium and Holland) numbered several million soldiers and were equipped with modern weapons, were defeated within ten days. There were several reasons for this rapid defeat. Firstly, the German army was mobile and fast, and effectively combining ground and air forces according to the combat doctrine of the "blitzkrieg". Above all, it managed to surprise the French army by bypassing the Maginot line, and attacking Belgium through the Ardennes Forests, considered impassable to armored units. 2 of the 9 German armored divisions invaded through the Ardennes. The French were certain that the line of fortifications on the German border was impregnable and so the army was complacent and captive to this concept.
Another reason was the lack of reserve forces and the dispersion of most of the armored amongst the infantry divisions. Above all, the French suffered from a weak Supreme Command, full of out-dated concepts, and unable to cope with the cruel test of war.
France itself was divided between Right and Left, national morale was at low ebb, and leadership was weak. The army was involved in politics and suffered from these squabbles. Although numerically the army was a stronger than the German army, it was much under the influence of fear of the German army going back to the previous World War. In addition to a number of combat squadrons sent by Britain to France with considerable risk to itself, nine divisions were sent from the England to the front in France, despite its own very meager military resources at the time. With the fall of Belgium and due to the little likelihood of stopping the German onslaught, it began to withdraw troops from France. Churchill, who had visited France several times and examined the situation at the front himself, thought correctly that the fall of France was inevitable and therefore preferred to preserve Britain's forces for the fateful day that was sure to come.
The Maginot Line
The Maginot Line was a line of concrete fortifications, tank obstacles, positions for artillery and machine guns and other fortifications that France had built along its borders with Germany and Italy following the First World War. In general, the Maginot line refers to France's defensive system against Germany, with the Alps forming the line of defense on the French-Italian border. The French believed that, thanks to the fortifications, they would gain the time required for their army to deploy defensively at the Front in the event of a German attack and this would compensate them for their numerical inferiority. The success of the static defensive battle in the First World War was the main influencing factor on the French way of thinking.
The defensive approach was first proposed by the Minister of Defense, Marshal Joffre, who was opposed by modernists such as Paul Reynaud, Finance Minister in 1938 and Prime Minister in 1940 and Charles de Gaulle, who preferred the offensive approach which called for investment in armor and aircraft. Joffre received the support of Petain and the subject remained controversial in the French government for a long time. Finally, Andre Maginot persuaded the government to invest in the defensive program. Maginot was an army veteran and a First World War veteran who became France's Minister for Military Affairs and later Minister of War (1928-1932).
The STG Section Technique du Genie (Department of Engineering Planning) under the supervision of the Commission d’Organization des Regions Fortifiers (Commission for the Organization Fortified Region) built the line in a number of phases from 1930. The main construction was largely completed by 1935 at a cost of about 3 billion francs. The specification of the fortifications was very high, with a complex system of interconnected bunkers adapted to thousands of people, there were 108 fortresses at intervals of 15 km, along with smaller fortresses and spaces between them and over 100 km of tunnels.
The line of fortifications was not planned to pass through the Ardennes Forest, an area considered impenetrable and impassable to large military forces. Furthermore there was no advanced planning to defend the French-Belgian border. The two countries signed an alliance in 1920, according to which the French army would operate in Belgium only in the event that German forces invaded there earlier. When Belgium unilaterally canceled the alliance with France in 1936 and declared her neutrality, the Maginot line was quickly extended along the French-Belgian border, but not on the same standard as the rest of the line. Another final effort of construction was made in 1939-1940 with general improvements throughout the line. The final line was the strongest around the industrial zones of Metz, Lauter, and Alsace, while other sectors were relatively weak. In reality, finally the Maginot line contributed nothing to France's security, and even harmed it as it formed the basis of an exaggerated, misguided and disastrous, defense concept.