As per title - I've been wondering for some time how expected the initial invasion was from the point of view of the Polish, especially those living in the areas that were occupied in the first few and days and nights.
Thanks!
Well, Polish high command started partial hidden mobilisation yet in March 1939 (shortly after German occupation of Czechoslovakia). 4 infantry divisions and 1 cavalry brigade were mobilised yet in March. During August (13-18) yet another 9 divisions were mobilised. On August 23rd started hidden mobilisation of main Polish forces (all according to mobilisation plan W). Thye've planned to announce open mobilisation on August 29th, but were persuaded by France and Britain to delay it till August 31st. Still by September 1st 60% of Polish troops were mobilised.
So yeah, invasion was highly expected and anticipated.
Cajus Becker interviewed an unnamed, captured Polish Air Force major in October 1939, as part of the Luftwaffe's attempt to learn all that they could from the Polish campaign. "The German Luftwaffe did exactly what we expected. It attacked our airfields and tried to wipe out our aircraft on the ground. It was quite naïve of the Germans to have believed we would leave our units sitting in their peace-time locations. By August 31st, not a single serviceable aircraft remained on them. In the previous 48 hours, all of us had been transferred to emergency airstrips. As a result, the Luftwaffe's opening blast completely failed in its purpose". Yet, there is a myth that the Germans destroyed the Polish Air Force on the ground on September 1st. It is not as widespread as the myth that the Polish army charged German Panzers with cavalry welding lances, but it is mentioned in many pre 1975 books about World War II.
Source: "The Luftwaffe War Diaries" by Cajus Becker
Everyone knew Germany was going to attack Poland, once it became clear that Hitler couldn't be appeased with small territorial concessions it became obvious that he was going to attack Poland as he wanted the Polish corridor and other regions of Poland. The exact date of the attack was a surprise, but most military planners knew the general date of the attack because on August 27th a small group of German soldiers attacked a Polish border post (they were unaware the offensive had been postponed to September 1st). The attack began at just before 5 a.m so most ordinary people wouldn't have known what was going on.