How did Starfleet crew its ships during the Dominion War? Romulan Senator Vrenak said the were encountering a manpower shortage and that was comparatively early in the war.
It makes sense. Training can be truncated but starships are highly technical and with new ship construction as well as losses, training new crew and especially officers would have been an extraordinarily difficult and time consuming. The Dominion could breed more Jem'Hadar but how could the Federation cope with the demands of war?