Poor weather and limited equipment will reduce the efficiency of your logistics system. You’ll also be able to capture enemy railways as you move into their territory, strangling their supply lines and redirecting trains to supply your troops. The total supply generated will depend upon the size of your industrial base, with railways acting as bottlenecks, limiting the amount of supply that can be distributed across regions if you don't construct enough train cars to shift the goods. Supply will flow from your nation’s capital, along railways, to be distributed from cities, naval bases, or manually constructed supply hubs to your divisions.
In the new system, railways will take on greater importance in your logistical infrastructure. Release dates for the update and DLC are yet to be announced. A dev diary posted to the Paradox Forum yesterday confirmed that both will focus on the Eastern Front, and revealed details of a major shake-up to the game's supply system and land warfare. More details of Hearts of Iron 4's upcoming free 1.11 Barbarossa update and as-yet-unannounced expansion have been revealed.
