Supply lines are roads, rail, and other transportation infrastructure needed to replenish the consumables that a military unit requires to function in the field.
Modern military units consume large quantities of such consumables and can be rendered combat-ineffective in hours or days if supplies are interdicted. This vulnerability has led many military leaders to build doctrine around indirect approaches to the enemy from the rear or above. These have been known as: "envelopment", "vernichtungsgedanken", "blitzkrieg", "hyperwar", and other forms.
Napoleon's army, plagued by hunger, cold, and poor supplylines, was forced to retreat.
Despite the siege and the bombings, the construction of Moscow's metro system, which began in the early 1930s, continued through the war and by the end of the war several new metro lines were opened.
The Sukharev Tower, as well as numerous mansions and stores lining the major streets, and various works of religious architecture, such as the Kazan Cathedral and the Cathedral of Christ the Saviour, were all destroyed during Stalin's rule.