September 17th, 1939 - the day Soviet Russia attacked Poland
September 1st, 1939 is the day on which - Poland and Germany agree - World War 2 started. The Polish call it September Campaign, the Germans - Fall White.
Poland was a militarily strong country for one that was coming out of a deep economical crisis. At first Hitler wanted to ally with Poland before attacking France. Yet, when Nazi German minister Ribbentrop tried to sign a military pact with Poland, Polish minister Beck replied that there is no way in hell Poland would be co-working with a monster.
That’s when Ribbentrop went to sign a secret pact with Soviet minister Molotov, instead - Nazi Germany alone was too weak to deal with Poland. Polish intelligence was one of the best ones in the world, too, so the secret pact was reported - but the head of intelligence laid it on the pile with diversion attempts, for he deemed an idea of those two set-against-each-other ideologies co-operating absurd.
Poland was a formidable enemy, but Hitler was arrogant. Originally, he planned to win Fall White after four days, and didn’t count on having to send reinforcements. (To compare: the rest of countries of continental Europe lasted from few hours to four days.) At first, the German army could barely move into the Polish borders by land, even though the cities were bombarded from the air. On September the 3rd Hitler send a telegram to Stalin to “hurry, and move already.” On the 5th Stalin send an answer “we aren’t ready yet.” It’s said that Hitler had a fit.
Fall White was planned by military doctrine only and it failed to take into account both human factor and the nature. Many Polish military posts were keeping defence for longer that it was theoretically possible. The Poles were blowing out the bridges. German tanks couldn’t move through the rivers, between the trees of thick forests, and were getting stuck in the mud (the Polish tanks were much better suited for that kind of terrain) - the German soldiers had to steal (or rather - catch from the wild, as the land-owner freed them upon the news of war) specially trained small horses (looking like ponies, really) to move those tanks anywhere.
Polish military knew the terrain. The Germans repeatedly reported higher numbers of the Polish units than existed, for horses could swiftly transport the soldiers between one battle and another through the terrain that was inaccessible to mechanical vehicles. Once Germans accidentally caught such a transport-column mid-way, so they recorded it and made a propaganda movie of “the Poles attacking German tanks with swords.” In reality, such an attack happened once - the Polish unit won enough of place to pass through due to a sheer astonishment of the Germans. In reality, commander of one of the Polish units that was forced to surrender due to running out of ammunition - had learnt from his German counterpart that 10 days more, and the Germans would be forced to back off because… they would run out of ammunition.
Speaking of horses, there was a horse-riding unit send from Prussia, probably as a challenge to rematch after the Grunwald battle (1410) - it didn’t make it to Nazi propaganda, because when the Poles took the challenge, the Prussian horse unit was trashed by the Polish horse unit.
From where the Polish army moved out due to strategical reasons, the volunteer Polish Scouts and civilians took their place and held the Germans back for as long as they could. Even single rooms were bastions worth defending. Also, they were army volunteers who single-handedly held German units back, by using the smoke and noise to create an illusion of Polish units being there. (All the people mentioned in this paragraph were aware that those were suicidal missions.)
It is said that the German intelligence messed with the Air Force strategy, for the communication was scrambled and they had trouble coordinating the strategy; it’s theorised that if not for some counter-productive messages, the Air Force could have been able to push Nazi Germany not only back to its borders, but even a bit farther.
All that time everyone was waiting for the promised help of the other Allied countries. All the Polish strategy was centred around receiving reinforcement from France and Britain. All that time it seemed that France and Britain will come to fight within a day or two.
On September 17th, Soviet Russia attacked. Russia entered the terrain where the strategic stuff was moved for safety from the Nazis… The Polish high command came up with that crazy plan of setting the Soviets against the Nazis. They issued an order to “not fight the Russians unless attacked.” The Russians were also given an order to not make a mess (they were to make an impression of heroes coming to help,) but they attacked many places non-the-less, plundering and raping - and so the people fought back in those places. (The Poles tend to lynch unconvinced rapists.)
The Poles described the Red Army as so dirty that they didn’t look like soldiers (it was customary for Polish soldiers to polish their shoes and equipment excessively), but coming in uncountable numbers. They also kept explaining to the Poles in very simplified terms things like what sugar is (it was like explaining to an American what coffee is) - for the shops were closed because of the war.
Straight away, the Russians sorted out the Polish intellectual class (all the Polish officers were intellectuals) by their soft hands -if your skin wasn’t hard from repetitive physical work, you would qualify - made a show of arresting them as “Nazi spies,” and sent them to the East some time later. The Poles complied, taking a guess that a war between Nazi Germany and Soviet Russia was bound to soon become a reality - and that the Soviet Russia would be desperate for good strategists, then. But before it happened, the Poles were all executed, about 200 000 of them. The Nazis targeted the elite in a similarly genocidal manner, though they looked that elite up by documents, not hands.
Poland never surrendered.