Why did the American Aircraft Carriers depart Pearl Harbor shortly before the attack?

I’m assuming training, but where did they go? What did they do?

Carrier locations, 7 December 1941

As stated, Lexington was delivering Marine fliers to Midway, and Enterprise was returning from a similar mission to Wake. *Saratoga *was picking up her air group in San Diego.

(If it hadn’t been for bad weather, Enterprise would have arrived in Pearl the afternoon of the 6th. Og only knows what the first year of the war would have been like without the Big E.)

Answer found here. >>> http://www.history.navy.mil/faqs/faq66-9.htm

There were only three Air craft carriers in the Pacific Fleet.

Two were on route from Hawaii toward Japan,

  • one to Wake Island and one to Midway Island, to ferry air craft to those bases.

The third was at San Diego , picking up air craft,crew, etc, coming up to fully ready after being in dock.

The fourth ? Well , it wasn’t part of the Pacific Fleet at the time but was rapidly transferred in the days after the PH attacks.

I’m not sure what you mean when you say the carriers departed “shortly” before the attack. The Enterprise had left Pearl Harbor on November 28. The Lexington left on December 5. And the Saratoga had been getting refitted back on the mainland since January.

These answer it; thanks guys. :slight_smile:

Looks like OP 's question has been answered, but just curious…Did the Japanese not know somehow that the aircraft carriers were out of port? Seems like easy intel to acquire.

Did they think it made little difference because they considered battleships to be more important prey? Since they were using aircraft carriers themselves, I wouldn’t think that was the case.

Why didn’t the Japanese wait until all the aircraft carriers were at port at Pearl to strike?

No they wanted the carriers more than the BBs. They did not if the carriers were in port or not. And waiting was not an option. Sunday Morning the fleet would be in port and just getting up. Monday morning and the fleet would probably be up and moving going out on training exercises. Also If they were discovered at sea that close to Hawaii the surprise would have been gone.

The battleships were the important prey. With the advantage of hindsight it’s clear that the aircraft carrier was more decisive of a weapon than the battleship during WW2 but at the time both the Japanese and the American admiralties still considered the battleship the more decisive of the two. The British attack upon the Italian battleships at Taranto, upon which the idea to strike at Pearl Harbor was based, was conducted with carrier aircraft but the British still considered the battleship to be the weapon of decision at sea, as did the Italians who didn’t even have an aircraft carrier.

As a side note, that the battleship had been dethroned by the aircraft carrier as the queen of the sea didn’t mean the battleship was obsolete, just that it was no longer the most important ship type in the fleet. During the war more of Japan’s battleships were lost to surface combat than to aircraft; 5 of the 6 US battleships that fought at Surigao Strait during which two Japanese battleships were sunk in October 1944 had been at Pearl Harbor.

They couldn’t. The Japanese had left port on November 28 operating under radio silence. They could not afford to loiter at strike range around Hawaii as they were bound to be detected sooner or later, they didn’t have the fuel to be able to do it anyway, and finally the attack on Pearl Harbor was being timed to occur at the same time Japan was launching attacks throughout the Pacific, from Hong Kong to Wake Island to Malaya to the Philippines, so even if the attack could be delayed the advantage of surprise would have been lost.

Also just to note, the “carriers not being at Pearl” is often used as evidence of a conspiracy that FDR knew of the attack beforehand and made sure the carriers were away. The locations of the Lexington and Enterprise, the only two carriers deployed at sea in the Pacific on Dec 7, 1941 was not where you’d want them to be if the idea was to keep them out of harm’s way. Either one could potentially have run across the return path of the Japanese carrier strike force and found herself alone and outnumbered 6-1.

IIRC, more Japanese tonnage was sunk by U.S. submarines than either.

Was sinking cargo ships part of the primary combat mission for Navy aircraft?

The primary combat objective would be to cripple the enemy’s ability to wage war. That would certainly include the destruction of resources useful to the enemy, so cargo ships would be a legitimate target.

Sinking cargo ships and transport ships were a very popular pastime. Dissonance was speaking only of battleships though, and I was speaking of total tonnage lost by the Japanese in WWII. Sorry for the confusion.

Also, read Gordon Prange’s At Dawn We Slept for a good account of the history of the Pearl Harbor attack. Japanese intelligence in Hawaii was hideously unreliable - both the consulate, and a single agent (IIRC, a non-Japanese dentist - maybe German? Would have to look it up to see.) Although they passed on an accurate grid map of Pearl Harbor, they were frequently misreporting the number and types of ships in the harbor, at one point reporting more capital ships were in the harbor than the US Navy owned in 1941.
After reading a bit of history, both of the Cold War and WWII, it’s notable how many spies just make nonsense up (or at least just thought they could,) send it to their superiors, and get paid. It must have been a pretty cushy job before the higher-ups could get satellite imagery to see if you were even doing the most rudimentary bits of work for the money.

Competent spies (who get written about more often) seem to be the exception rather than the rule, the Japanese agents in Hawaii in 1941 were not exceptional, and probably not competent.

Also, one might want to remember the attack was supposed to be synchronized with the Japanese Ambassador in Wash DC delivering a diplomatic note to the US Secretary of State. As it turned out, it took the weekend duty Japanese embassy staff much longer to decode and type out the note than expected, and the note ended up being delivered after the attack had taken place.

Furthering the “why didn’t they wait” question, and unlike our Navy’s capability today, the Japanese ability to replenish at sea was all but non-existent.

As to the realization that battleships had become dinosaurs, it became apparent following Midway, and maybe even prior to Midway following the battle of the Coral Sea. The U.S. Had plans to build a new class of battleships (Montana Class) very early in the 1940s. In fact the boilers and turbines were procured and a hull designed for the first of this class. Ultimately it was decided to scrap the idea of a new battleship. The aforementioned procurements, to include the hull design, we’re used to build the USS Midway (CV41), the construction of which took less than two years (thanks to the availability of the boilers, turbines and design).

Also remember the Japanese ships were traveling under radio silence-- even if the Japanese had some last-minute intel on the location of the carriers, they had no way of communicating that to the fleet. Their communication consisted of signaling each other with lights and flags, nothing else.

It couldn’t have gotten much worse. They probably would have transferred another carrier over from the Atlantic fleet, I guess.

As a note, the US was making active preparations for war and busily starting fortifications. The Japanese couldn’t afford to wait even 6 months.

IJN strategy called for a “decisive battle,” kantei ketteisen in which the IJN fleet would defeat the USN fleet. They hoped to weaken the fleet at Pearl Harbor and also wanted to use their carriers and subs in a similar role.

There was actually split thinking within the Japanese command. Admiral Yamamoto, for all the forward thinking he’s created with, was planning more on defeating the US battleships, and believed that the loss of the battleships would destroy US morale. The commander Genda who actually created the plan wanted to target the carriers, and devoted a higher ratio of planes to target them. (And of course, the Naval General Staff believed that attack was risky and was opposed.)

As quibble, Japanese sources place the beginning of the planning for the attack prior to Taranto. It had certainly been war gamed by both sides in 1940 and before.

Further expanding his point, at that battle, those battleships were stationary and the IJN fleet came to them. The reason that the battleships were at dock in Pearl Harbor was that they were too slow to accompany the carriers.

The problem with sinking battleships by planes was that it was damn hard. Their armor was too think for dive bombers’ munitions to penetrate and torpedo bombers were especially vulnerable to CAP. The Japanese used specially designed bombs in their attack at Pearl Harbor for the battleships on the inner row, where the torpedoes couldn’t reach, which would not have been successful against a ship at sea.

The Japanese military and the foreign services famously did not get along, and did not trust each other. Well, actually the military didn’t trust each other, with the IJA and IJN also not sharing information with each other.

Correct, also the problem was that the diplomats had to type it out themselves instead of using the secretary pool. Another problem was that the embassy wasn’t given the ultimatum until the last moment and Tokyo grossly underestimated the length of time required.

Of course, since the US could decode the message faster than the embassy, had it been sent any earlier then that would have just given the US more time to prepare.

There already was a recognition of air power prior to the start of the war. The Two Ocean Act of 1940 called for more carriers than battleships.

This isn’t correct. Radio silence means that the fleet did not send messages. They could have received them.

Regardless, there simply was no way for the fleet to hang around Hawaii waters any longer than absolutely necessary. They had to attack on a Sunday morning and they could only attack what was there.

Because they were at Pearl Harbor, six of the eight battleships attacked at Pearl Harbor eventually saw military service, mainly shelling Japanese held countries. So even this didn’t really help Japan.

 I really all countries can do really stupid things but was Japan's decision to attack Pearl Harbor in hopes that America would lift the oil and steel embargo and stay out is about the stupidest thing ever? 

Did they ever hear about Fort Sumter? Alright, 4 days later Hitler decided he declare war on America without getting Japan to fight Russia.