What naval logistics must sustain

Naval logistics covers far more than fuel tankers. A fleet needs fuel, water, ammunition, food, spare stores, and sometimes specialist support. Vessels able to replenish at sea can greatly extend a squadron's time on station. British supply ships applied the same principle during the Napoleonic Wars, allowing warships to remain off French and Spanish ports until maintenance, rather than consumables, forced them home. By 1939, navies were still managing the transition from coal to oil alongside several generations of machinery. The size and quality of the support system determined fleet endurance as surely as the number of fighting ships.