[Huliwang]

Most definitely this is a prelude to an impending Russian attack on the West's supply line

These huge quantities of weapons arrive in Poland by hundreds of containers and shipped to the frontlines in the east by trains. They make easy targets for Russian Kalibr missiles. 

Warn -> Attack -> I did warn you

This is a very explosive situation here. I believe the Russians would have strike the weapon cargoes bound for Ukraine if the cargoes are transported by sea or air through international sea or air space. 

I think the Russians are holding back because the weapons are moving into Ukraine through Poland, a NATO member country. Striking those cargoes while on enroute through Poland would tantamount to attacking Poland which would enlarge the war. The Russians can only strike those cargoes once they crossed the border of Poland but currently the Russians have yet to take control. 
So either the US stop the weapon shipment after this warning or risk getting into this war with Russia. The stakes in this poker are getting higher.....