From the attack on Poland to the occupation of Denmark and Norway: As a result of the numerical and above all armed forces superiority as well as the concentration of the majority of the German army and air forces in the east and the passivity of the Western powers persisting in the “seated war” behind the Maginot Line, which themselves are still insufficient were armed and overestimated the military strength of Germany, the military conquest of Poland succeeded in a short time. Right at the beginning of the invasion of the Wehrmacht, the Polish authorities had around 10,000 to 15,000 “ethnic Germans” arrested according to prepared lists – probably out of fear of an uprising of the German minority; around 4,000 of them fell victim to riots (around 1,100 on “Bromberg Bloody Sunday”, Bromberg).

Supported by two strong air fleets (1,538 aircraft), which quickly gained control of the air, two German Army Groups, Army Group South ( G. von Rundstedt) from Silesia and Slovakia and Army Group North (F. von Bock) advanced from East Prussia and Pomerania in a pincer attack on Warsaw and destroyed the strongest Polish force group in the Battle of the Bzura (9-19 September 1939). After the Polish government and the high command had ceded to Romanian territory, on September 17, Soviet troops advanced into eastern Poland and advanced as far as the Vistula; the government of the USSR justified this military action – also demanded by the German side – with the assertion that in the face of the collapse of the Polish state it was being carried out “to protect” the Belarusian and Ukrainian population there (afterwards these areas were annexed after the Polish-Soviet War fell to Poland in 1921, to the Belarusian and Ukrainian SSR). Officially, the Soviet government remained neutral.

According to indexdotcom.com, Warsaw surrendered to the German troops on 27/28. 9th, Modlin on September 29th On September 30th, 1939 a Polish government in exile was constituted in Paris under General W. Sikorski, which (after stops in Angers and Bordeaux) moved its seat to London in June 1940. The last military resistance in Poland was extinguished on October 6, 1939. The losses of the Polish army amounted to 66,300 dead, the German 10,500 dead. Around 694,000 Poles were captured by Germans and around 230,000 by Soviets. About 100,000 soldiers managed to flee across the borders to Hungary, Romania, Lithuania or Latvia; many of them continued their struggle in the ranks of the Allies.

On the basis of the German-Soviet border and friendship treaty signed in Moscow on September 28, 1939 (amending the agreements of August 23, 1939), Lithuania was now also assigned to the Soviet sphere of interest; the German part of the Polish territory, however, was extended to the Bug. After the incorporation of Danzig, West Prussia, Poznan and considerable old Polish territories into the German Reich (“integrated eastern territories”) and the establishment of the General Government (Governor General H. Frank) in the winter of 1939/40, with the systematic extermination of the intelligentsia, the National Socialist occupation policy, which brutally treated the Poles as “subhumans”, began from the remaining Polish territory. Poles from the annexed eastern regions were deported to the General Government or deported to Germany for forced labor. The Polish Jews were brought together in large gettos (including Warsaw) and later mostly murdered in extermination camps.

Around 1.5 million people (including the Polish ruling class) were deported from eastern Poland, which was annexed by the USSR. Most of the 14,500 Polish officers captured by the Red Army were murdered by members of the Soviet NKVD in 1940 on behalf of Stalin (Katyn). As a result of forced assistance pacts with Estonia, Latvia and Lithuania, the Soviet government set up bases for its armed forces in these countries in October 1939 in order to prepare for the “annexation” of the Baltic states to the USSR (occupation in June 1940, annexation in August 1940). Efforts to open Finland to Soviet influence and to obtain the cession of bases and border areas (especially in the area of ​​Leningrad) failed because of the refusal of the Finnish government. Therefore, on November 30, 1939, the USSR opened combat operations against Finland (Finnish-Soviet winter war) without a declaration of war, but initially failed to achieve its goals after surprising military defensive successes by the Finns (including persistent defense of the “Mannerheim Line”).

Meanwhile, Great Britain and France were planning to open secondary theaters of war in Scandinavia and the Balkans, and were considering air strikes on the Baku oil area, considering the USSR an ally of the German Empire. After his “peace appeal” of October 6, 1939 (calling for recognition of the status quo in East Central Europe) remained unsuccessful, Hitler pushed on a military decision against France in November 1939. However, the bad weather situation, concerns of the generals (including the lack of ammunition after the end of the fighting in Poland) and the disagreement in the Wehrmacht leadership regarding the attack plan forced the attack to be postponed several times to spring 1940 A crisis of confidence broke out between the army command, which feared a failure of the offensive and a positional war, and Hitler, which led to the verge of a coup d’état.