If the crew had been experienced, personnel might have closed openings more quickly, operated portable pumps better, and communicated the severity earlier.
If Abe had slowed immediately, less water might have been driven into the damaged hull.
If pumping systems had been complete, progressive leakage might have been controlled more effectively.
If Archerfish had scored only one hit, all the internal weakness might never have mattered.
The sinking required the attack to intersect with the ship's unfinished state.
That intersection is the real answer.
The six-hour chase mattered as much as the six torpedoes
Archerfish's success is sometimes compressed into one firing sequence.
That understates Enright's achievement.
The submarine had to remain in contact with a faster surface force for more than six hours.
Losing visual or radar contact could end the opportunity.
Surfacing brought exposure.
Submerging reduced speed.
The escorts could force the submarine away at any time.
Enright therefore had to predict where Shinano would be rather than simply chase where she had been.
This is classic submarine interception.
A submarine attacks geometry before it attacks a ship.
The commanding officer must calculate target course, speed, bearing, range, and future position.
He then moves to the location from which torpedoes can cross that future path.
Archerfish finally reached that location.
The carrier's course change then created an unusually favorable attack angle.
The torpedo hits therefore began with hours of patient positioning.
The final 1,400-yard shot lasted only minutes.
The real attack had begun much earlier.
Enright also had a personal history behind the opportunity
Joseph Enright's career adds another layer to the attack.
Before Archerfish, he had commanded USS Dace.
During an earlier patrol, Enright had faced an opportunity against the Japanese carrier Shokaku but did not achieve the attack he wanted. He subsequently requested relief from command after believing he had not acted aggressively enough.
He later received another command.
That second opportunity was Archerfish.
U.S. Navy historical accounts note this earlier episode when describing his eventual success against Shinano.
The contrast is striking.
A commander who had once left a carrier encounter dissatisfied later found the largest carrier in the world.
This time he pursued for hours.
He placed the submarine inside the escort formation's threat environment.
He fired every available bow tube.
Then he went deep.
The result became one of the greatest single successes in submarine warfare.
The shallow torpedo setting was especially important
Enright's decision to run the torpedoes shallow deserves attention.
A large ship presents many potential target depths.
A torpedo that runs too deep may explode against underwater protection where the hull is designed to absorb damage.
A shallow hit can open the side near the waterline and promote asymmetric flooding.
Shinano's anti-torpedo bulges provided significant protection lower on the hull.
The American torpedoes struck higher.
U.S. Navy analysis specifically emphasizes this vulnerable zone.
This did not mean the torpedo-defense design was useless.
It meant protection is geometrically limited.
A submarine commander who understands the relationship between torpedo depth and target construction can improve the effect dramatically.
Enright did not know every detail of Shinano's design.
He did not know he was firing at a Yamato conversion.
His shallow settings nonetheless produced exactly the kind of flooding threat most dangerous to a large ship whose internal watertight condition was compromised.
Chance and skill met again.
The escort destroyers could punish Archerfish but could not reverse the attack
After the torpedoes hit, Shinano's destroyers attempted to find the submarine.
Archerfish went deep.
Depth charges followed.
The submarine survived.
This phase reveals the limits of escort protection.
Destroyers can make submarine attacks dangerous.
They can force submarines away.
They can sink them.
What they cannot do is recall torpedoes already in the water.
Once Enright had achieved his firing position, the escort battle became secondary.
The destroyers' mission shifted from prevention to retaliation.
They failed to destroy Archerfish.
Then they faced a new role.
They had to help the carrier.
Later they attempted towing and rescued survivors.
An escort formation can therefore transform within minutes from defensive screen to rescue force.
Shinano's destroyers experienced exactly that change.
They had left Yokosuka expecting to guard the largest carrier in the world.
By late morning they were collecting men from the sea where the carrier had disappeared.
The loss was especially humiliating because Shinano had barely begun her career
Shinano was commissioned on November 19.
She sank on November 29.
Her operational life lasted only ten days.
She never conducted normal carrier combat operations.
She never launched a major air strike.
She never joined the kind of fleet action for which so much steel and labor had been invested.
Much of her final voyage was essentially part of her completion process.