Archerfish destroyed both before they reached their destination.
Shinano's loss did not decide the Pacific War
The sinking was dramatic.
It did not change the war in the way Midway or the Philippine Sea had changed it.
Japan's naval aviation was already severely weakened.
Shinano alone could not restore the trained air groups lost during years of war.
A carrier without sufficient skilled pilots and aircraft cannot produce the combat effect suggested by its tonnage.
Even if Shinano had reached Kure and become fully operational, Japan would still have faced overwhelming American industrial and naval superiority.
This context prevents exaggeration.
Archerfish achieved an extraordinary tactical success.
It destroyed a unique strategic asset.
It did not single-handedly alter the outcome of the Pacific War.
The value of the story lies elsewhere.
It demonstrates how a small submarine could exploit the vulnerability of an enormous capital ship.
It demonstrates the importance of readiness.
It demonstrates that unfinished systems can negate impressive design features.
It demonstrates that damage control is part of combat power.
The Japanese investigation focused on exactly those issues
After the loss, Japan convened an investigation.
Postwar U.S. analyses drew heavily on findings from that inquiry.
The conclusions did not suggest that four torpedoes simply contained enough explosive power to defeat 72,000 tons by themselves.
The investigation emphasized the condition of the ship, the poor watertight integrity, deficiencies in damage control, and decisions made after the attack.
A later U.S. Naval Institute discussion summarized the accepted lesson clearly: Shinano's rapid loss resulted from both poor damage-control performance by an untrained crew and the failure to achieve proper watertight security in the unfinished carrier.
That is the answer to the historical mystery.
The ship's giant displacement delayed the result.
It could not correct the underlying deficiencies.
Why continuing at 18 knots mattered so much
One of the most discussed decisions concerns Abe's choice to maintain substantial speed after the torpedoes hit.
A postwar U.S. Naval Institute analysis states that the carrier continued at roughly 18 knots for a period after the attack.
Think about what that means physically.
The damaged starboard side is moving through the sea at more than 20 miles per hour.
Openings in the hull are being forced against water.
Water entering those openings is not simply responding to static pressure from the ship's draft.
Forward motion adds dynamic pressure.
Every damaged boundary behind the opening must cope with the resulting inflow.
If the internal ship were perfectly subdivided, continued speed might still be acceptable temporarily depending on the damage.
Shinano was not perfectly subdivided.
Moving fast helped water reach openings farther inside.
By the time the true scale of flooding became clear, slowing the ship could not remove the water already aboard.
This illustrates how a reasonable tactical instinct can become dangerous when based on incorrect information.
Abe believed he commanded an extraordinarily resistant ship.
He did not know how badly incomplete construction had compromised its internal ability to isolate damage.
Damage reports probably arrived slower than the flooding
Large ships create communication problems during emergencies.
The bridge cannot see underwater compartments.
The captain depends on reports.
Damage-control stations depend on messengers, telephones, sound-powered circuits, and local officers.
After multiple torpedo hits, those communications may be disrupted.
Personnel below may understand the seriousness before senior officers above do.
Postwar descriptions of Shinano suggest precisely this gap.
From the bridge, the carrier was still moving.
Below decks, water was advancing through spaces that damage-control personnel could not effectively isolate.
The outward appearance of survival therefore lagged behind the internal reality.
This is another recurring pattern in ship disasters.
The captain may not receive one dramatic message saying the ship will sink.
Instead, reports accumulate.
Another compartment flooded.
Another pump failed.
Another bulkhead leaked.
Another machinery space became unusable.
Eventually the collection of local problems becomes a global conclusion.
Shinano crossed that point over several hours.
The decision to counter-flood traded time for buoyancy
Flooding the port-side boiler spaces helped reduce the starboard list.
That was valuable because an extreme list can cause rapid loss.
However, counter-flooding is not free.
The additional water lowered the ship deeper into the sea.
This reduces freeboard.
Openings move closer to the water.
The margin before deck-edge immersion shrinks.
The ship becomes heavier.
In a stable, completed vessel with controlled damage, counter-flooding can be exactly the right action.
In Shinano, uncontrolled flooding continued after the correction.
The additional deliberate water therefore became part of the growing total.
The list might temporarily look better while overall survivability continued worsening.
This demonstrates why damage control requires accurate information about the entire ship.
Correcting one visible symptom can make another problem worse if the underlying flood rate remains unknown.
The loss of propulsion marked the beginning of the final stage
As long as Shinano could move under her own power, there remained hope of reaching safer water.
The moment she went dead in the water, that hope collapsed dramatically.
According to U.S. Navy history, the carrier had managed to travel roughly 36 miles after the torpedo attack before boiler-feed problems brought her to a stop.