3 April 1939. Wehrmacht High Command issued a directive "On the Unified Training of Armed Forces for War", containing the main provisions of the preparations for the upcoming war with Poland. The main task of the ground forces imposed in the directive was the complete destruction of the Polish armed forces before a possible third party could enter the war. For this purpose, it was prescribed to prepare for waging a “blitzkrieg” - a sudden massive strike that would lead to the complete superiority of the Wehrmacht until the enemy completed the mobilization measures. The directive provided for the OPPORTUNITY to begin operations from the twentieth of August 1939.
Geographically, Germany had all the prerequisites for achieving a quick victory over Poland, which seemed to be in a semi-circle, since East Prussia hung over its territory from the northeast, and the annexation of Czechoslovakia allowed them to use Slovakia for a massive invasion from the south. This configuration of the front line enabled the Wehrmacht to deliver a powerful blow by large forces in converging directions. It was not difficult to foresee (for those military leaders who then wanted to think) that the German command would conduct military operations in Poland with two or even three army groups, using the natural-geographical position. But for some reason, the Polish command believed that a possible German offensive would develop along only one path. However, more on that later.
To fight the German command created two army groups, "North" and "South". Their very name speaks of their deployment sites.
The North Army Group, commanded by Colonel-General von Bock, included the 4-I and 3-I armies. Before them was tasked with joint strikes from East Prussia and Pomerania to establish a link between East Prussia and Germany. Subsequently, they were supposed to defeat the enemy defending north of the Vistula by concerted actions of all forces, and then, in cooperation with Army Group South, destroy the Polish units, which would remain in the western part of Poland. From the bend of the rivers Oder and Varta, only small forces were to attack in order to pin down Polish troops here and to deceive the enemy.

The entry of German troops in Poland. September 1 Morning 1939
German tank part in the region of Mzlopolsk, September 5, 1939
German soldier in battle. 5-6 September 1939
Army Group South, under the command of Colonel-General von Rundstedt, included the 14, 10 and 8 armies and, having concentrated powerful forces in the offensive zone of the 10 army, from the Silesia region in the general direction of Warsaw, defeating the Polish troops standing against it. Having forced the Vistula on the both sides of Warsaw and surrounding the capital of Poland, they, in cooperation with Army Group North, were supposed to complete the destruction of the remaining Polish troops and go either to the border with the USSR or (if the Russians would nevertheless decide to start fighting against Poland) - to connect with the units of the Red Army.
In total, 44 divisions were concentrated for the offensive against Poland, mainly personnel divisions, including tank and motorized divisions. In addition, on September 1, the formation of another 10 reserve divisions began, which did not take part in the hostilities. The German Air Force in this theater of operations totaled up to 2 aircraft, reduced to the 1st Air Fleet under the command of the general aviation Kesselring (Army Group North) and the 4th Air Fleet under the command of General Aviation Lehr (Army Group South).

German anti-aircraft SDU SdKfz 10 / 5 in battle. Poland, 1 1 September 1939
Commander SdKfz 222 overcomes the stream along the bridge.
Street fight in Bydgoszcz.
German automobile part on the march to Warsaw. 6 September 1939
Note that before the war, Poland was not considered a small state. Its population in 1939 was over 35 million, people, and the army was very large for peacetime - 30 infantry divisions, 1 cavalry division and individual cavalry brigades (more than 1 million). Equipment of the Polish Armed Forces weapons it was sufficient, but its samples (weapons) were products of mostly obsolete types. There were few tanks; and of these, only 7TR more or less met modern requirements and was taken into account by the Germans. The Renault R3S and Hotchiss H35 hooks received from France were not put into operation (according to the negligence of the command, even Polish instructions were not made for them, which made their development by the troops almost hopeless). Of the thousands of small planes that made up the Polish air force, less than half (and those bombers) could be considered more or less modern. The field artillery mainly consisted of 75-mm and 76-mm 1890-1920 quick-fire guns. Anti-tank artillery was quite modern, but extremely small. Even less were anti-aircraft artillery, the development of which, as well as the development of fighter aircraft, was completely neglected in Poland before the war.
Misses in equipping and recruiting the Polish armed forces were aggravated by strategic miscalculations of the Polish command. Given the current situation, Poland could count on success in defending its own territory only by withdrawing the main forces for the Vistula, San and Narev and erecting additional fortifications there. But at the same time, the industrial area of Upper East Silesia would have to be given to the Germans, and therefore the Polish command, with its great power of thinking, would see such a retreat incredible. The commander of the Polish armed forces, Marshal Rydz-Smigly, set himself an absolutely insoluble task. Like his French teachers, he wanted to keep the entire territory of Poland with existing forces, and to take even swift offensive actions against East Prussia. The principle of “we will not give up our land” prevailed before the war in the defensive doctrine of almost all European countries. Therefore, the main forces of the Polish army (like the armies of other countries) were located along the borders in order to repel the first blow of the aggressor to quickly go on the offensive and "beat the enemy in its territory with a little blood with a powerful blow." In addition, the Polish command believed that France, faithful to its allied duty, would certainly strike Germany from the rear, which in this case was threatened by a “child mate in three moves”.
Thus, a real chance to transfer military operations with Germany to a positional war on previously prepared lines was ignored, and Poland was unable to carry on maneuverable battles with existing forces. So the war was deliberately lost by the Polish command long before September 1939.
We intend to omit here the Gleuitsky incident, repeatedly described over fifty years of post-war history, and proceed to the course of military operations.
The Polish command (as well as the command of many European countries) expected that the war would begin in accordance with the traditions, from border clashes and battles, during which small forces from both sides would take part, gradually involving larger masses of troops in the fighting and therefore did not hurry With the general mobilization announced by 20 in August, the latent mobilization of the Polish government began in March 1939. The strategic deployment of troops provided for in the mobilization plan for the start of hostilities did not Chenoa and hit many parts of the German units of the Polish army took while on the move or on time, or not equipped positions.
PzKpfw IV Ausl A in the Modlin area. September 1939
Trophy Polish tank A11 Mark I, surrounded by German soldiers.

The surrender of the Polish troops of the group "Modlin". 21 September 1939
The commander of the German tank unit accepts the surrender of Polish officers. September 1939
German troops, in accordance with the “blitzkrieg” doctrine (the authorship of which some authors attribute to the Soviet Union for some reason), crossed the Polish border 1 September 1939 in 4 hours 45 minutes in the morning. Simultaneous performance of all ground troops massive strikes on Polish airfields inflicted Luftwaffe units. Despite the mobilization and preparations for war by the Polish command, the Polish aircraft were completely open, many of them were not fueled, did not carry weapons, and therefore the aircraft of the defenders quickly ceased to exist.
The actions of the ground forces developed in strict accordance with a pre-developed scenario. Despite the adventurousness of some points of this scenario, the German offensive unfolded, in general, successfully. The impression of failure to capture the bridge in Dirschau (the Poles managed to blow up the bridge, which delayed the attackers for a short time) and the action of the landing group in Westerplatte (the Germans unexpectedly met with fierce resistance) were slightly spoiled. Despite the guarantees of the Allies, it was only on the morning of the third day of hostilities that the British and French put forward an ultimatum to the Germans, and declared a war for dinner. But no active actions, despite the numerous promises of the Polish command, did not begin. Moreover, all the fears of Hitler that the allies, even without crossing the border, would be able to limit themselves to effective actions of their own aircraft and fleets against the territory of Germany, did not materialize, as K. Zibert, who commanded the cover company of the West Wall, testified, France, barked, fell asleep.
Army Group North took only a few days to establish a connection between East Prussia and Germany. After the battles in the Tukholska Wasteland with two Polish infantry divisions and a cavalry brigade attempting to counter-attack and defend here, the 4 I left the September 4 in the Kulma area and forced the Vistula. In the course of the battles, more than 16 LLC people were captured with 100 guns. Part of the 3 Army, advancing from East Prussia, 4 September broke into the northern fort of the fortress Grudzionz and the next day the fortress fell. By September 7, advanced units of the army reached the Narew River, destroying a large enemy force in the area north of Mlawa on the way.
The 14 Army of Army Group South with meager losses seized the Upper Silesian industrial region, simply bypassing the Polish fortifications that were here.
The 10 Army, which included several tank divisions, already advanced 2 September to the Warta River north of Czestochowa, then turned to Warsaw and Radom. 7 September 10 army was already in 60 km south-west of Warsaw.
5-6 September revealed that the calculation of the required quantity of ammunition and artillery for combat operations was, to put it mildly, insufficient, as well as the fact that German planes and tanks consume gasoline somewhat more than that guaranteed by the manufacturers. But if the situation with gasoline was still tolerable, then diesel fuel catastrophically came to an end. In order to allow diesel trucks to move around, 6 September was hastily designed an instruction for replacing diesel fuel with a mixture of synthetic gasoline and crude oil. Increasingly, aviation was used to supply the troops. 6-7 September 1939 were critical days of the entire Polish campaign.
By September 7, the covering forces of all Polish border defense areas were shot down and destroyed, or carried out a random departure. The control of the Polish armed forces under the blows of the German troops became impossible, but despite this, Polish soldiers fought everywhere with extreme bitterness, although their command was completely stupid, which led mostly to unjustifiably high losses. September 6 The Polish government hastily left Warsaw and moved to Lublin, from which September September 9 left for Kremenets, and September September 13 went to Zalishchyky. 16 September the Polish government crossed the border of Romania. The army was left without command; the country was left to the mercy of fate.
Street fighting in the suburbs of Warsaw.
German flamethrowers suppress the Polish firing point. September, 1939
German aircraft bombed Warsaw. September, 1939
Calculation of the German 20mm anti-aircraft gun on the Opera Square in Warsaw.
Calculation of the German howitzer in street fighting in Warsaw.
Further operations of the German army led to the encirclement and destruction of all those still bleeding in the defense west of the Vistula, Polish units. In spite of the obvious outcome of this defense, Polish soldiers continued to fight at times with despair, reaching the point of recklessness. By September 10 the battles here were over. Then the 3-I and 14-I German armies took offensive action east of the Vistula. They delivered deep strikes from the north and south in order to surround the Polish reserve units that were here. 14 army actions were simplified by the fact that 5 September and the war entered Slovakia, which advanced one division, crossed the border at Dukel Pass. The 14 units of the army met at the San River with a strong defense, which 9-10 of September was broken north of Sanok. On September 11, formations of the right flank of the 14 army crossed the river, completing the bypass and encirclement of Przemysl.
The connections of the left flank of the 14 Army, after the capture of Krakow, advanced on both sides of the upper course of the Vistula and then crossed to the eastern bank of the river in the Sandomierz region. Then the crossing over San and the exit to Rawa-Russkaya, where the advancing units clashed with a large group of Polish troops, was carried out. These were the remnants of the Polish armies that had departed here from the southern border. Commanded these units General Pistor. The group had fierce resistance to the German troops and inflicted heavy losses, but nevertheless, by September 16 it was surrounded, and soon destroyed.
10-I army, forcing Warth, 13 September surrounded a large group of Polish troops in the Radon area, creating a boiler to which more than 65 thousand people and 145 guns were “welded”. After several days of fighting, the remnants of five Polish divisions stationed there were captured. The left wing of the 10 Army, meanwhile, continued to advance toward Warsaw. Already on September 11, its advanced tank units began fighting in the suburbs of the Polish capital, but all their attacks were repelled.
These days for the German troops created a new critical situation on the northern flank of the 8-th army, reflected in the 10-th army. It was created because the 4 infantry divisions and 2 cavalry brigade of the army "Poznan", which the Polish command planned to use for conducting offensive operations in Germany and who were not involved in defensive battles, began to retreat in the general direction of Warsaw. Along the way, Polish troops met the highly stretched German 30 Division, which was providing the northern flank of the 8 Army, advancing on Lodz. Polish troops turned south and attacked the German division on a broad front, which was in a difficult position. Other Polish units, randomly retreating in the direction of Warsaw, joined with the Poznań group and strengthened it. 8-I army was forced to turn to the north and go on the defensive. The 10 Army units, which received orders to attack the Polish group from the east, also suspended their offensive. The units of the 4 Army received orders to surround the Poles also from the north. But before the encirclement was completed, units of the German 8 Army had to be tight, as units of the Poznan group continuously attacked them with the despair of a mortally wounded beast. This lasted from 8 but September 11, after which the Polish units themselves went on the defensive, from time to time trying to break through south. On September 16, they made a final attempt to break free from the German ring in the Lovich area, after which their resistance was broken. September 19 remnants of nineteen divisions and three cavalry brigades, only about 170 thousand people, led by General Bortnovsky, laid down their arms.

17,19. A. Hitler examines the destroyed Polish armored train.

German tank PzKpfw II Ausf with lined in the suburbs of Warsaw.
The parade of German troops in Warsaw.
While fighting with the group "Poznan", the German 3-I army followed the Guderian tank corps (redeployed to gain it) east of the Vistula. September 9 army crossed the Narew and rushed to the south, 11 September it almost without obstacles from the Polish army forced the Bug, and beating Warsaw from the east, turned through Siedlce to the west to finally surround the capital, while Guderian's mobile connections continued to move southeast. One forward detachment broke through the September 14 line of Brest forts and made its way to the citadel. But the resistance of the garrison was broken only 17 September with the approach of the main forces.
On September 13, the Osovets fortress in northeastern Poland passed into the hands of German troops. It now remained to surround Warsaw from the west, which was soon done.
September 17 decided to enter the war the Soviet Union. Moving quickly in front of the Red Army, 21 September broke down organized resistance wherever it flared up and soon met with the advance units of the German army. However, the “Red Blitzkrieg” (and, most likely, maneuvers, which were sometimes fired with live ammunition) is a topic that deserves a separate description.
September 19 Polish campaign was virtually over. Warsaw, despite numerous German ultimatums and memoranda, continued desperate resistance, but the defenders thawed under the air and artillery strikes of 21 in September at the suggestion of the German command, representatives of all diplomatic missions and more 1 200 foreigners were evacuated from the city, and the city fell on 28 in September. September 30 capitulated Modlin fortress, and October 2 stopped fierce resistance and the last stronghold of the Poles - the port of Hel.
In a war that lasted only 18 days (the siege of Warsaw is not counted), the Polish army was completely destroyed. Approximately 695 thousand people were captured by the Germans, up to 217 thousand people by the Russians. It is possible that, before 100, thousands of people fled across the borders of Romania, Hungary and Lithuania. The huge number of killed Polish soldiers and civilians who fought alongside them, according to some sources, is more than one and a half million people, and most likely will never be precisely established.
The German Armed Forces successfully completed the first stage of their blitzkrieg. Despite the fact that they were opposed by a fairly numerous adversary, the operation developed almost without deviations from the scenario. The losses of the German army were miserable: 10 572 people killed, 30 222 wounded and 3-109 missing. But all these successes were to a large extent determined by the illiterate leadership of the Polish command and the hurray and patriotic mood of the population before the war, with the complete silence of the Polish allies. Despite the fact that the Polish campaign was studied by representatives of the military intelligence services of many countries, no one has drawn the right conclusions from it. The French, the British, the Russians and the Americans were all victims of a reassessment of their own forces and succumbed to complacency. To make them so big and strong some Germans (or Japs) attacked ... Never in my life! But they attacked, and suddenly it turned out that such big and strong (Americans, British, Russians, French ...) were absolutely not ready for war and paid for it at a very high price. Sometimes exorbitant.
But the German command did not take any lessons from the past campaign. It was after Poland that Hitler believed in the absolute infallibility of the military doctrine of the Third Reich and the reliability of the Wehrmacht military machine. And the tested template “went into circulation” throughout all subsequent campaigns, and when it was time to relearn, there was not enough time for that.