The continued presence of older battleships does not mean all of them remain fully commissioned. A viable reserve consists of ships kept in good repair and capable of at least secondary wartime duties. A small core crew, possibly less than ten percent of the full complement, keeps machinery and systems working. Trained civilian reservists periodically return for exercises and supply the rest of the crew on mobilization. Because they already have training, reservists can be assigned more deliberately than people brought in through emergency conscription. The arrangement preserves useful combat capacity without paying for full peacetime manning across the entire fleet.
Notable Point · 2:00-4:05
How a fleet reserve preserves wartime capacity
The Royal Navy's large pre-dreadnought total leads into an explanation of maintained reserve ships, core crews, and trained reservists.