Originally posted by
SunilTanna
If Germany attacks France, it's perfectly possible that Poland doesn't get involved.
I disagree. Poland would have got involved. Their logic would have been simple - our best ally is France; without France we are pretty much alone against USSR and/or Germany; if France goes down, so do we; since Germans are focused on France we can hit them in the back, to help our ally at relatively little cost; if we do nothing and France fails - we go down; if we do nothing and France wins - the French are angry with us for not keeping our part of the alliance; if we attack and fail - well, at least we tried; if we attack and win - so the better.
In short - it is in Poland's interest to help Polish allies attacked by the common enemy, since if they go down, Poland is next to be invaded and is all alone.
Now, how effective Polish actions would have been, that is completely different question. IMHO the best choice for the Poles would have been to attack Silesia, perhaps also East Prussia.
Silesia - an important industrial region with significant Polish population which might become useful; taking Silesia might do some real damage to German war effort (not that much, but still). There are some fortifications, but no too many, at least not in Upper Silesia.
East Prussia - also some Polish (or at least Polish speaking) population and the region is like a dagger hanging over Warsaw; problem is the region is quite well fortified (even if the fortifications are a little old) and relatively easy to defend thanks to many rivers and lakes.
The march straight onto Berlin might be considered a little too dangerous - Poles would have had to deal with exposed wings and some significant fortifications in the way (Ostwall). OTOH, that migth seriously force Germans to withdrew some forces from the west and help the western allies.
Polish abilities: 30 infantry divisions, 9-10 reserve infantry divisions, 11 cavalry brigades, 2 motorized brigades (1 not fully operational), relatively weak artillery, rather weak air force with obsolete fighters and some decent bombers. Also ~ 80 batalions of Obrona Narodowa (National Defence) - something similar to British Home Guard, although some batalions were almost as strong as regular army units. ON might be useful for protecting communication lines and acting as occupying units. Polish Navy was very weak comparing to Kriegsmarine so it wasn't able to act offensively.
Personally I would use most of the regular units (20 divisions, most of the cavalry and artillery) to attack Silesia; 5 regular divisions and some cavalry would act as reserve; 2 regular and 4 reserve divisions might try knocking at East Prussian front; the rest covers the rest of the border with ON acting also as human reserve for front troops.
Of course a lot depends of the forces Germans have left to protect their eastern border, but considering that they go against one of the most powerful armies in the world (i.e. the French Army) they need to hit the west as strong as they can. So there isn't much left to keep Poland in check.
I think Polish Army might achieve some success in Silesia, probably occupying the Upper Silesia, possibly also reaching Breslau (today Wrocław). East Prussia might be harder to crush but it can be somewhat neutralized. However, even the logistics might not allow the Poles to go much further - AFAIR Polish ammunition supplies and all other strategic materials reserves were relatively small; allied supplies via Romania might help, but not too much.
And there is also a tiny detail called the Union of Soviet Socialist Republics...