Six bow tubes did not require an S-class commander to fire all six weapons or even the commonly encouraged four-torpedo salvo. Some commanders preferred spreads of three or two according to target, opportunity, and their desired reserve. With twelve weapons, three-torpedo salvos increased the theoretical number of full attacks from three to four. The choice therefore balanced hit probability in the immediate attack against endurance across a patrol.
Notable Point · 59:22-1:00:06
Why submarine commanders varied torpedo salvo size
Sturgeon's three-torpedo attacks frame the tradeoff between maximizing one attack's probability and preserving weapons for more engagements.