It's a myth that Polish cavalry charged German tanks. In fact the Polish military were not mobilised when the Germans rolled in, so the defence was not supported by light artillery forward and heavy artillery in the rear, with infantry manning strong points and cavalry held in reserve to support weakening points and/or attack vulnerable extended supply lines... but the German generals didn't know for sure that the political maneuvering would create the degree of surprise it did, hence the tanks did not go charging in as massed armour but [SIZE=14.3999996185303px]advanced accompanied, unsurprisingly, by their panzer grenadiers. So if the romantic myth had even a shred of truth, it would have been the German infantry whom the Polish cavalry charged. But it never happened.[/SIZE]
Some Polish cavalry units did participate in ad hoc attempts to defend against a German Armoured Division, they used their horses as transport to get to the battlefield, not to charge futilely into machinegun fire waving sabres. After all, the Polish were not especially blind or stupid whilst WW1 raged across Europe. Their military contained cavalry regiments, but they were geared up to fight trench warfare, like everyone else except the Germans, who had decided (correctly as it turned out) that the way to prevent a short term stalemate followed by a long term war of attrition was Blitzkrieg. But remember, only the panzer grenadiers were mechanised infantry, the rest of the German army also used horses for transport.
Edit to add: why oh why does this fucking forum 'ware constantly select random bits of text for a font size rebellion?