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The Planning of Pearl Harbor

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On this date in 1941, the Imperial Japanese Navy launched an incredibly daring, technically sophisticated combined naval-aerial surprise attack on the U.S. naval base at Pearl Harbor, just northwest of Honolulu on the Hawaiian island of Oahu. The devastating aerial attack carried out by Japanese fighters, dive-bombers and torpedo planes crippled the U.S. Pacific fleet as a preamble to Imperial Japan’s lunge for strategic territories spanning the Pacific Ocean – but it also stirred the wrath of the American people, decisively ending U.S. isolationism and bringing the world’s largest industrial power squarely into the war against Japan and its European allies in Nazi Germany and Fascist Italy.

The Economic Vise

Pearl Harbor was born of strategic desperation. Over the previous couple years, Japan and the U.S. had been engaged in a tit-for-tat diplomatic and economic struggle, as the Roosevelt administration tried to restrain escalating Japanese aggression with embargoes on raw materials crucial for the Japanese war machine. Japan was heavily dependent on American supplies of oil and metal, with American shipments accounting for 80% of Japan’s oil and copper imports and almost half of its scrap iron imports.

Over several years the U.S. tightened the economic vise, responding to Japanese aggression in China and Southeast Asia by cutting off supplies of aircraft materials in 1939, scrap steel in 1940, and machine tools and metal ore in 1941. The final blow came with the suspension of oil deliveries in summer 1941.

At first, the Japanese hoped to negotiate their way out of the American economic embargo, but the Americans’ unwavering opposition to Japanese foreign policy convinced the Japanese leadership that further negotiation would be fruitless. They decided instead to deliver a knockout blow to the U.S. Pacific fleet with a surprise attack on Pearl Harbor, which would, they calculated, give Japan two years of unchallenged supremacy in the Pacific and a window in which they could conquer the oil-rich Dutch East Indies (today Indonesia) and the rubber plantations of Malaya. This, in turn, would give Japan enough resources to fight on once the U.S. rebuilt its Pacific fleet.

The odds were steep, to say the least. The plan required bringing a huge aircraft carrier battle fleet – comprised of six carriers, two battleships, and 48 combat and support vessels including cruisers, destroyers, submarines and tankers – 4,000 miles from the northeast coast of Japan to Pacific waters north of Hawaii in complete radio silence, a feat akin to smuggling an elephant through airport security. Ships in the attack fleet couldn’t communicate with home base, meaning there was no way to call off the attack without exposing their position.

Uphill Battle

In fact, the man in charge of planning the attack – the brilliant admiral Isoroku Yamamato, who had studied in the U.S. and respected American fighting spirit – advised against it, noting that even if it succeeded, Japan would still face an implacable enemy drawing on huge resources. He famously warned:

“Should hostilities once break out between Japan and the United States, it would not be enough that we take Guam and the Philippines, nor even Hawaii and San Francisco. To make victory certain, we would have to march into Washington and dictate the terms of peace in the White House. I wonder if our politicians (who speak so lightly of a Japanese-American war) have confidence as to the final outcome and are prepared to make the necessary sacrifices.”

But the hyper-nationalists in charge of Japan could not imagine submitting to what they perceived as American bullying, and decided on war, no matter how desperate, and no matter how steep the price. The die was cast.

After leaving Japan on November 26, the Japanese fleet steamed east across the Pacific, reaching a point about a thousand miles north of Hawaii on December 3. During their silent run, the Japanese ships were scattered by a sudden Pacific storm that lasted two days, stringing them out over hundreds miles of open water – but still managed to regroup with minimal use of short-range, low-power radio to communicate their positions, a remarkable feat of seamanship and navigation. Then from December 4-6, the fleet headed south until it reached a staging point a few hundred miles north of Oahu in the early morning hours of December 7.

Here the attack shifted from its naval phase to the aerial phase, with two waves of dive-bombers, fighters, and torpedo planes taking off from the carriers beginning at 6:10 a.m. Hawaii time. The first bombs fell at 7:48 a.m. Surprise was complete, as the operators of the primitive American radar mistook the approaching Japanese planes for a returning flight of U.S. B-17s.

Assisted by some ineffectual midget submarines, over two hours and 20 minutes 354 Japanese planes sank four American battleships, damaged three more and caused the last to run aground, while damaging or destroying ten other ships and over three hundred aircraft. The human toll came to 2,402 killed and 1,247 wounded, including 1,177 dead aboard the U.S.S. Arizona, the hardest-hit. Japanese losses were light, reflecting their success in achieving total surprise. Meanwhile Japanese forces fanned out across the Pacific, with near-simultaneous attacks on American forces in the Philippines and Guam, and tiny colonial garrisons in the Dutch East Indies and Malaya.

Although the attack was devastatingly successful, it was not the knockout blow Japanese planners had intended. Most importantly, the U.S. Navy’s Pacific carrier fleet was left untouched, since all three aircraft carriers were at sea during the attack. These would provide a crucial counterbalance to Japanese naval power in the Pacific in 1942, beginning with the stunning American victory at the battle of Midway.

Photo: George Strock/TIME & LIFE Pictures

Worse, the Japanese leadership badly miscalculated in their long-term strategy. In particular, they were over-optimistic about their ability to secure the long maritime supply lines from the oil wells of the East Indies to Japan; these proved vulnerable to American submarines, which helped strangle the Japanese economy in the final years of the war.

Last but not least, the effect on American morale was essentially the opposite of what the Japanese hoped. In the weeks following Pearl Harbor (which included Adolf Hitler’s declaration of war on the U.S. on December 11), approximately one million American men volunteered for military duty. This would be followed by a draft that eventually built the American military into 12-million-strong juggernaut by 1944, compared with Japan’s 4.3 million men in military service by the end of the war.

Thanks to LIFE.com for the photo. See more rare Pearl Harbor pictures here. This post originally appeared in 2011.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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