The French attack on Germany between September 19th and October 16th was a minor conflict in the Second World War. It was part of a French plan to divert the Germans attention from the Polish front and take Munich. In this, the invasion failed in both, as it failed to significantly reduce pressure on the by then already collapsing Poland and was beaten off well before Munich.
Bold text== The French invasion: September 19th to 28th 1939 == France's initial attacks into western Germany met surprisingly with next to no resistance. The three divisions defending Freiburg were soon forced to retreat from the province under intense French pressure. France entered the city on September 22nd, but did not press home their attack for a crucial three days. On September 24th, Poland, battered and weak from the German and Soviet invasion, surrendered. This allowed the Germans to bring thousands of troops from the east to the west. Despite this on September 28th, French troops entered Friedrichshafen and began attacking east towards Munich.
The German response: September 23rd to October 2nd 1939
With a large portion of its garrison attacking Munich, the defences of the Maginot Line were severely compromised. Major General Rommel, seeing this weakness, launched an attack along with several panzer divisions south from Stuggart, capturing Strasbourg on September 30th. At this point, several French commanders began to request permission to withdraw back towards Mulhouse. The French government quickly overruled them and instead ordered them to continue their offensive against Munich.
Operation: Eagle in the West
On October 3rd, German forces under Rommel began an offensive against Mulhouse, code named 'Unternemun Adler im Westen', a move which would cut the French in Germany off from supply and in the words of Hitler, "Allow the Germany army to divide and conquer." Surprised French forces resisted stubbornly and the French commanders began a large scale withdrawal eastward from Germany. the French Tanks were more heavily Armoured and armed compared to the German tanks, but French tactics were woefully inferior. However, Rommel's forces, after initially slow progress, smashed through the French lines and captured Mulhouse, trapping a huge section of the French army (nearly 50 divisions) in a pocket. Operation: EitW had been an unqualified success story.
The battle of the Freiburg Pocket: October 7th 1939
French commanders in the pocket were ordered to wait for relief, however, it never came and instead, the Germans began the largest battle of the war so far to pound the pocket into nothing. Most German commanders expected it to take about four days, it took less than twenty hours for the Germans to take Freiburg. The French continued to fight, but the invasion was now unsalvageable and the last French troops in the pocket surrendered on October 15th.
The cost to France was massive, close to fifty divisions were lost and the Maginot Line was made completely worthless. Germany was in a much stronger position, having wiped out its only major land enemy. Britain sued for peace on November 17th, ensuring Germany's final victory over France in the summer of 1940. However, Hitler was not contented with just that victory and he turned east in 1941, invading the Soviet Union. At first, victory seemed to be close, but the Soviets slowly ground the Germans to pieces. The defeats at Stalingrad in 1943 and the Kursk Salient in 1944 sealed the Germans fate and on April 30th, with the Soviets closing around Berlin, Hitler committed suicide. With Germany defeated, Stalin effectively ruled the whole of northern Eurasia, from the Pacific to the Atlantic and from the Arctic Ocean to Mediterranean Sea. Even as early as the end of 1946, it was clear Stalin was planning an invasion of Britain and Spain, helped no doubt by a new German super weapon, the nuclear bomb.