The North Koreans relied on a logistical system which was very lean and substantially smaller than the UN system. This logistics network was therefore capable of moving far fewer supplies, and this caused considerable difficulty for front-line troops. Based on the efficient Soviet Army model, this ground-based network relied primarily on railroads to transport supplies to the front while troops transported those items to the individual units on foot, trucks, or carts. This second effort, though more versatile, was also a substantial disadvantage because it was less efficient and often too slow to follow the moving front-line units.