4.45 am on September 1st, 1939, German battleship Schleswig-Holstein attacks the Polish garrison of the Westerplatte Fort, Danzig.
September 2nd, 1939:
-Poland asks for assistance from Britain and France; the two nations respond by declaring war against Hitler and demands the Nazi's to withdraw from Poland.
-Canada, India, New Zealand, Australia makes declarations of war.
September 3rd, 1939:
Winston Churchill named the leader of Britain
Britain and France Declares war against Germany.
September 5th, 1939:
The Nazi take over the city of Krakow.
September 6th, 1939:
Groups of the Wehrmacht gathered at the city of Lodz, centre of Poland and has divided Poland up into two; this leaves Poland trapped against the German border.
September 8th, 1939:
Hopes are failing for the Panzers of Poland, and only hope clings onto the British and French relief that was asked for.
September 13th, 1939:
The French Army bails out to the Maginot line for further national security.
September 15th, 1939:
Warsaw is bombed severely.
September 17th, 1939:
Soviet Union enters the east Polish border in accordance to the Nazi-Soviet Pact.
2:00 PM, September 27th, 1939:
Warsaw is taken over. Poland suffers full invasion.
October 3rd, 1939:
The invasion ends when Poland is divided up between Germany and the Soviet Union.
The German invasion of Poland was the basic start to the Second World War. Before this invasion occurred, the leaders of Europe were concluding that Nazi-Germany won't keep peace and would use force to take over Europe, therefore believing that Germany cannot be stopped through nothing, but through the same way. When Hitler invades Poland, it gives reason for the rest of Europe for the most part(disregarding Hitler's allies like Italy) to use strength against Hitler. As a result, the Second World War which can possibly be considered the 'inevitable' war, began.
When, Hitler decided to put through the invasion, the Germans disagreed in that their army wasn't fully strengthened to full power, and that when the army is away in the east, Britain and France might strike. However, Hitler still carried it out believing that the Polish invasion would be and that the Chamberlain (Britain) and Daladier (France) would not try to declare war, but try to keep peace in the first place.
Hitler was able to not expect attacks from Britain and France in that he had won some of the revision of the Treaty of Versailles; the two nations accepted the rearmament of Hitler, rearming of the Rhineland, take over German side of Czechoslovakia and in general, made the two nations and the whole Europe afraid of the rise of Germany. Moreover, some of the Powers positively regarded Germany's rearmament in that it could be a way to defend Stalin and the Soviet Union's influence.
Britain and France does declare war against Germany in 1939, but does not have any impact in that they are not prepared to actually go to war and has to focus more on their national securities.
The only concern that Hitler had was Stalin whom Hitler believed would alarm through the invasion. The both sides, however, surprised the whole of Europe by signing the Nazi-Soviet Pact which signified each other's desire for personal gains.
Hitler then comfortably bombs the cities of Poland; Poland resists until the end, but eventually gives in when Warsaw is breached on September 27th, 1939.
Germany's four-week campaign in Poland results in massive casualties to both sides; 50,000 German soldiers were dead, injured or missing; Poland lost 70,000 soldiers and 130,000 were wounded with another 90,000 polish soldiers fleeing to the allies located close by like Hungary and Romania.
The invasion marks its end when on October 1st, 1939, when Poland is partitioned between Nazi-Germany and the Soviet Union.