Hello!
How high was the risk of Japanese invasion of the US main land? Any ideas?
Thanks!
The whole question what we could considered as USA main lands?North America?
The Phillipines was the lands of USA as i remember 
I believe there was a substantial threat to Hawaii for a time. If the Japanese could advance so far as to take Hawaii, then they would have been in a position to invade the mainland United States; namely California. This is why the Roosevelt administration had so many Japanese-Americans living in Hawaii and California interned; the people there were the most afraid of conflict with the Japanese and spies in their ranks. However, once the U.S. and Australia defeated Japan at the Battle of the Coral Sea and started to check their advance, this type of attack faded from the realm of reality.
High enough for U.S. to dig/build fortifications along coasts – At least public had to be calmed down
But from military point of view, it’s very difficult to supply such a large force (required for invasion) over a long distance (compare to troubles nazis had with crossing channel) - requires solid naval and aerial control among many requirements.
_
So do I understand correctly that the US goverment/army did not consider invasion to be possible in 1942?
I think invasion was still considered a remote possibility at the beginning of 1942, but as I said, after the U.S. and Australia defeated Japan at the Battle of the Coral Sea in May, and the U.S. again defeated Japan at the Battle of Midway, it was pretty much considered a non-issue.
The Japanese did invade the Alaskan islands and the US forces were on the highest alert possible.
On the alert for full scale landing (invasion) or the alert for the sabotage by the Japanese special forces?
Full scale invasion. They thought it was entirely possible since it was so close to Japan. However, Alaska was not officially a US state until 1959, so this may not count. Nonetheless, here’s a photo from my archive. Japanese attacks on Alaska:
Right. But I was thinking about the US west coast, not Alaska.
Did they internaly seriously considered to be possible in the goverment and the army center?
Invasion of the north American continent though possible was never a real threat. As mentioned earlier defenses were constructed mainly as a means of reassuring the population.
When you look at the logistics involved Japan could never have spared the resources necessary. They were trying to hold a land mass from New Guinea north and hundreds on individual islands.
The reasons why Japan attacked the US puzzles me. If America had not been dragged into WWII they would most likely have taken Australia (or part of Australia) As the British were willing to allow them in to the North and Australia had set up defenses on the infamous Brisbane line.
Less than zero.
Japan’s sole war aim, motivated by a range of domestic and international factors, was to secure resources and a Japanese-dominated trading bloc in East and South East Asia by the conquest of other nations and European colonies to implement the Greater East Asia Co-Prosperity Sphere.
The intention was to grab these lands and hold them until the rest of the world accepted Japan’s conquests. Exactly the same policy it had pursued in China in the preceding decade, and with much less chance of eventual success.
Conflict with the US was limited largely to ‘the decisive naval battle’ for control of the Pacific and the strategic necessity of taking the Philippines, Wake etc.
Inavasion of Hawaii was discussed but rejected.
Invasion of the US mainland (continental US) was never contemplated as Japan knew it was beyond its resources.
Nowhere in the primary sources is there any indication that Japan had the slightest intention of invading mainland USA. The Japanese were arrogant and over-confident in their pre-war and some 1942 assessments of their long term military and economic aims, but they weren’t insane.
Here are Japan’s war aims.
http://www.ibiblio.org/hyperwar/PTO/Dip/IR-410702.html
Mainland America was never even remotely anywhere near anything included in the three spheres of the co-prosperity sphere, although parts of Russia were. http://www.isop.ucla.edu/eas/restricted/geacps.htm
All very true. But hindsight is 20/20 and all that.
In fact, I believe the US gov’t did consider a Japanese invasion to be a remote possibility if not a serious threat. The “war nerves” on the west coast of the United States were at a level of borderline irrationality, and for good reason. No one had expected the Imperial Navy to launch a successful coup de main strike at Pearl Harbor either.
I think I’ve heard of a fanciful Japanese-German agreement to split up the US at the Mississippi River? While there were no serious plans for an invasion, the fear was still there…
As you point out, it’s important to distinguish between what was known then and now, and to distinguish between post-war knowledge and legitimate fears based on reasonable inferences from events during the war.
The Principal Historian at the Australian War Memorial has delivered a couple of odd papers arguing that, essentially because of what is known now about Japanese intentions and decisions, the Australian Prime Minister in the second half of 1942 deceived the nation by maintaining that there was a risk of Japanese invasion. Given the direction of Japan’s advance; hostile acts towards the Australian mainland; Tojo’s demands for Australia to surrender; and the Japanese going flat out in Papua - New Guinea and Guadalcanal on Australia’s doorstep, the Prime Minister and the rest of the Australian population weren’t exactly living in fantasy land by thinking they were at risk of Japanese invasion. We know now that Japan never approved operational plans for that invasion but, as Japan didn’t bother to inform the Australian government or people that it wasn’t going to invade, the belief was entirely reasonable at the time.
Americans were entitled to the same concerns about Japan attacking the American mainland, if not at quite the same acute level as Australians were with Japanese forces on our doorstep, given Japan’s hostile actions towards America.
The somewhat farcical Battle of Los Angeles in February 1942, a few days after a Japanese bombing raid about the same size as Pearl Harbor on Darwin in Australia’s north, demonstrates the level of defensive steps taken on the West Coast and the belief that America could be subject to Japanese attack. The Japanese invasion of American soil in the Aleutians in June 1942, like the Japanese invasion of Australian soil in Papua about a month later, was reasonable grounds for the inference that Japan had designs on continental America.
The fears in both nations were real, and justified at the time.
the belief that the japanese were coming was quite high on the west coast during the first six months of the war…it was exaserbated by the several instances of japanese submarines surfacing at several points along the west coast,(LA,near san francisco,and near portland) and doing a crappy job of shelling some inland targets with their deck guns and by serveral false air raids( the battle of los angeles was one of these…)…the invasion of the aleutians was seen as a possible first step by many in the media…life magazine even devoted a 20 page,“what if” pictorial ,in late '42,to how a japanese invasion of the US ,via alaska, would play out…i always liked the picture of the american gas station attendent geting shot by the japanese in a light tank he’s being forced to refuel,while he sprays burning gas all over the tank.
Possibly Noburo Fujita and IJN submarine I 25. Fujita had an extraordinary history of flying unchallenged over cities in Australia and New Zeanand from I 25 in wartime and then launching what I think is the only airborne bombing raid on the continental US. Alas, he bombed a forest. Not his fault. That was his mission, to set the land alight.
I had a much better link but can’t find it, so this Google result will have to do for a summary
http://www.wolfendenpublishing.com/haroldstephens/bangkokpost_japanamericanbomb.htm
There were also the fire balloons to set the US alight http://www.faqs.org/docs/air/avfusen.html
I dont belive that The Japanese military could mount an effective attack against the U.S. mainland. They didnt have the resources in materiel, or manpower to accomplish a landing that would be sustainable. Their forces would have been met, and encircled, or at least driven back into the sea. they would have lost their entire force.
They may have thought about a land invasion, but decided it was too great a risk to their ability to prosecute a war.
They would have found that upon arriving, not only were they under attack by the regular military based in the U.S. but also any Army reserve units that could be put to work against them. And lets not forget that America had then, as they do now, a very well armed, and at that time motivated civilian population. possessing most of the types of weapons in their homes, that the japanese infantry would likely possess. This would be one of the main reasons behind the existance of the second amendment to the U.S. constitution.I add that last paragraph for the benefit of those who may live outside the U.S.
- Raspenau -
The reason I made the thread was that I wanted to find out if the GOVERMENT of USA seriously considered invasion as a threat. What people think is one think. What the bosses think and therefor do afterwards is an other.
It was considered as a realistic possibility, but not necessarily a probability, early in the war. Military provision was made for such an eventuality, although it wasn’t all that good in a number of respects.
Until the Japanese attacked in the Pacific, the United States had counted on its Hawaiian bastion and on the Pacific fleet to provide a secure barrier against any serious attack on the continental west coast. After Pearl Harbor it seemed, at the outset, that this barrier had been broken and that the 1,300-mile length of the west coast could be attacked by the Japanese in strength and almost at will. The most vital installations along this coast were military aircraft factories that had sprung up during the prewar years at Los Angeles and San Diego in the south and at Seattle in the north. In December 1941 nearly half of the American military aircraft production (and almost all of the heavy bomber output) was coming from eight plants in the Los Angeles area. The naval yards and ship terminals in the Puget Sound, Portland, San Francisco Bay, Los Angeles, and San Diego areas, and the California oil industry were of only slightly less importance to the future conduct of the war. In the first two weeks of war it seemed more than conceivable that the Japanese could invade the coast in strength, and until June 1942 there appeared to be a really serious threat of attack by a Japanese carrier striking force. These calculated apprehensions were fanned in the first few days of war by a series of false reports of Japanese ships and planes on the very doorsteps of the Pacific states.7
–82–
This was the outlook that persuaded the War Department to establish the Western Defense Command as a theater of operations on 11 December and that led it to concentrate its first attention after Pearl Harbor on the rapid reinforcement of the Army’s ground and air garrisons along the west coast. When the war started, the Fourth Army had available fairly adequate harbor defense forces, 11 of the 12 infantry regiments allotted to it under the current RAINBOW 5 plan, and about 5 antiaircraft artillery regiments which lacked two-thirds of their equipment. The Second and Fourth Air Forces had only a fraction of their assigned strength in planes, and they were critically short of bombs and ammunition. During November and early December General DeWitt had requested more ground troops for defense purposes, but these were denied until the Japanese struck.8
On and after 7 December General Marshall and his staff worked feverishly to strengthen the west coast defenses as rapidly as they could. A pursuit group from Michigan began to arrive in the Los Angeles area on 8 December, but it was the reinforcement of antiaircraft artillery defenses that received the most attention during the week after Pearl Harbor. By 17 December nine additional antiaircraft regiments had been rushed from various parts of the United States to the west coast, and, with some assistance from Marine Corps units, the vital installations in the Seattle, Portland, San Francisco, Los Angeles, and San Diego areas were thereby provided with at least some antiaircraft artillery protection. The Army also moved two additional divisions and many lesser types of ground combat and service units to the west coast before the end of December and made the 3d Division, already there, available for defense use. As a result of these moves the Western theater’s major Army combat units in January and February 1942 included six infantry divisions, a brigade of cavalry, about fourteen antiaircraft regiments, and the equivalent of three pursuit and three bombardment groups. The troop strength of the Western Defense Command numbered about 250,000 at the beginning of February, and of these nine-tenths were ground troops. Approximately 100,000 of the ground forces were actively engaged in manning harbor antiaircraft defense equipment, in maintaining a beach and forward patrol along the coast line, in patrolling the
–83–
Southern Land Frontier, and in performing anti-sabotage duties at vital installations9
By the third week in December, as the pattern of Japanese operations and the disposition of Japanese naval forces became known, apprehensions about an imminent and serious attack on the west coast subsided.
http://www.ibiblio.org/hyperwar/USA/USA-WH-Guard/USA-WH-Guard-4.html
we also have…
California and the Second World War
The Shelling of Ellwood
On 23 February 1942. the Imperial Japanese Navy’s submarine I-17, under the command of Commander Nishino Kozo, surfaces shells the oil refinery near Santa Barbara. Before the war, as skipper of an oil tanker, Nishino had refueled there. The shelling does only minor damages to a pier and an oil well derrick, but creates “invasion” fears along the West Coast.Contemporary newspaper accounts describe the attack as off the Ellwood oil fields 12 miles north of Santa Barbara, and report 16 shells fired, beginning at 7:15 p.m. on the 23rd of February 1942. Three shells struck near the Bankline Co. oil refinery, the apparent target of the shelling. Rigging and pumping equipment at a well about 1,000 yards inland were destroyed but otherwise no damage was caused. One shell overshot the target by three miles and landed on the Tecolote ranch, where it exploded. Another landed on the nearby Staniff ranch, dug a hole five feet deep, but failed to explode. Eleven other shells fell short and dropped into the sea. Description of the attack and damage to the oil refinery was provided by the superindentent, F.W. Borden. The first report of the attack was called in to police by Mrs. George Heaney of San Marcos Pass, who observed the submarine through binoculars and reported it was about a mile offshore. Oil refinery worker Bob Miller also called in a report during the attack. According to the official report of the 11th Naval District, the I-17 surfaced at 7:10 pm, Pacific War Time (2 hours ahead of standard time, so about a half hour after sunset), shortly after President Roosevelt’s weekly fireside “chat” began. At 7:15 pm, the submarine began firing from its deck gun at the oil refinery. It ceased firing at 7:35 and departed on the surface; it was observed still on the suface exiting the south end of the Santa Barbara Channel at 8:30.
A 1982 issue of Parade magazine published a possible reason for the attack:
The first Japanese attack on the U.S. mainland, in 1942, was triggered by cactus spines in the rear end of a Japanese naval captain.
In the late 1930s, Kozo Nishino was commander of a Japanese tanker taking on crude oil at the Ellwood oil field. On the way up the path from the beach to a formal ceremony welcoming him and his crew, Nishino slipped and fell into a prickly-pear cactus. Workers on a nearby oil rig broke into guffaws at the sight of the proud commander having cactus spines plucked from his posterior. Then and there, the humiliated Nishino swore to get even.
He had to wait for war between the U.S. and Japan, but on Feb. 23, 1942, he got his revenge. From 7:07 to 7:45 p.m., he directed the shelling of the Ellwood oil field from his submarine, the I-17. Though about 24 shells were fired from a 5.5-inch deck gun, little damage was done. One rig needed a $500 repair job after the shelling, and one man was wounded while trying to defuse an unexploded shell.
U.S. planes gave chase to the sub, but Nishino got away. Thereafter, American coastal defenses were improved, so the mainland suffered only one more submarine attack by the Japanese during the war, at Fort Stevens in Oregon.
Most accounts however have the I-17 firing 16 17 rounds fired from 19:15 to 19:35 hours
http://www.militarymuseum.org/Ellwood.html
also…
Fire balloons
Between November 1944 and April 1945, Japan launched over 9,000 fire balloons toward the American mainland. Carried by the recently-discovered Pacific jet stream, they were to sail over the Pacific Ocean and land in North America, where the Japanese hoped they would start forest fires and wreak devastation. About three hundred were reported as reaching North America, but little damage was caused. Six people – five children and a woman, Elsie Mitchell – became the only deaths due to enemy action to occur on mainland America during World War II when one of the children tried to recover a balloon from a tree near Bly, Oregon and it exploded. Another landed in Omaha, Nebraska with little effect.[2] Recently released R.C.M.P. and Canadian military reports indicate that fire balloons got as far inland as the rural area near Ituna, Saskatchewan.