WI: Japan invaded Australia

What would have happened had Japan invaded Australia at some point during WWII? What reactions would come from the international community, including the U.S. and Britain? Obviously, the invasion could never have been permanently successful, but what would the long term results of such an invasion be like?
 
Logistically difficult before taking port moresby, but the success of the attempted offensive there was prevented by spirited defense and japanese equipment inadequacies, as well as the low priority the operation received. A japanese landing that wasn't immediately repulsed would have meant tying down anzac troops, as well denying to the americans a critical base of planning, raining, and logistics.
 
Ironically it would have looked a lot like a combination of Mad Max and LRDG running around in flying columns shooting up Japanese forces. Australia is a big place and they already had massive numbers of troops in China and SE Asia/Philippines, tacking on Oz too would have been a big logistics drain.

Probably the Commonwealth Forces/US would have set a up a defensive line somewhere to the East and try to hold onto Sydney, Brisbane, Melbourne and Adelaide in the East and South. Japanese logistics would have been awful, they would be at the end of a very long and vulnerable ocean supply line then the main method of moving goods would be ship and railway. The road net was pretty poor in the 1940's with few metaled roads and the rest being graded gravel and dirt, so moving anything on wheels would have been hard as it is unlikely the Australians would have left much wheeled transport behind or rolling stock for that matter.

Besides once the insect, snake, spider and jellyfish had gotten at them I expect most of them would give up in horror.
 
Japan's troops go into a hostle environment where the enemies strength and logistics are far away, if their lucky they die on the beaches if their not lucky they die horribly as they are whittled away by the environment and the australian army.
 
I'd find it hilarious if they tried to invade anywhere west of Darwin. Even today there is virtually no infrastructure beyond the odd town and the national highway system.
 
By the time invasion is possible Australia has the following Australian military formations are active and at home:

  • The 6th and 7th Divisions, both AIF, home from North Africa
  • Remains of the 8th Division, AIF, recuperating after heavy losses in Malaya
  • 1st Armoured, active since July 1941, achieved full OOB May 1942.
  • The 1st, 2nd, 3rd and 4th Divisions, Citizen Military Forces, active though with some sub-units deployed to New Guinea.
  • The 3rd Motorized/Cavalry (name depends on the exact date...), Citizen Military Forces, active.
  • The 2nd Armoured Division, Citizen Military Forces, forming
  • The 6th, 10th and 12th Divisions, Citizen Military Forces, forming.
  • Plus various other bits and pieces about the place.
So, just counting Australian troops, that's 6-9 infantry divisions depending on the exact date of the invasion; 2 armoured divisions and one motorized division. There also the possibility of bringing the 8th Division back from North Africa early.

In terms of American forces in Australia...

  • The 32nd Infantry Division arrived in April-May 1942.
  • The 6th Infantry Division arrived in April 1942.
So, that's 8-12 infantry divisions, 2 armoured divisions and one motorized division available.

Japanese sealift means they're hard pressed to bring more than 3 or, if really stretching things, 4 divisions to the game.

Yeah, unless the Japanese land in the Middle of Nowhere, NT/Far North Queensland the landing goes squish quickly. If they do land Middle of Nowhere, well, it's a self supporting PoW camp until supplies run out, thereafter the landing ceases to be a problem... unless the Salt Water Crocs get 'em first.
;)
 
By the time invasion is possible Australia has the following Australian military formations are active and at home:

  • The 6th and 7th Divisions, both AIF, home from North Africa
  • Remains of the 8th Division, AIF, recuperating after heavy losses in Malaya
  • 1st Armoured, active since July 1941, achieved full OOB May 1942.
  • The 1st, 2nd, 3rd and 4th Divisions, Citizen Military Forces, active though with some sub-units deployed to New Guinea.
  • The 3rd Motorized/Cavalry (name depends on the exact date...), Citizen Military Forces, active.
  • The 2nd Armoured Division, Citizen Military Forces, forming
  • The 6th, 10th and 12th Divisions, Citizen Military Forces, forming.
  • Plus various other bits and pieces about the place.
So, just counting Australian troops, that's 6-9 infantry divisions depending on the exact date of the invasion; 2 armoured divisions and one motorized division. There also the possibility of bringing the 8th Division back from North Africa early.

In terms of American forces in Australia...

  • The 32nd Infantry Division arrived in April-May 1942.
  • The 6th Infantry Division arrived in April 1942.
So, that's 8-12 infantry divisions, 2 armoured divisions and one motorized division available.

Japanese sealift means they're hard pressed to bring more than 3 or, if really stretching things, 4 divisions to the game.

Yeah, unless the Japanese land in the Middle of Nowhere, NT/Far North Queensland the landing goes squish quickly. If they do land Middle of Nowhere, well, it's a self supporting PoW camp until supplies run out, thereafter the landing ceases to be a problem... unless the Salt Water Crocs get 'em first.
;)


They can do foraging by hunting.... Kangeroo. Make sure not to bbq it but to make a slow cooked stew. Or it will be as stiff as rubber.
 
I know that I will run contrary to some of the opinions above but...

... seriously, it's Australia. They don't even need soldiers to defend the place when they've got killer emus(*) and taipan snakes and gympie bushes and box jellyfishes and saltwater crocodlies and Atrax spiders and platypi.

(*) known to be actually militarily superior to the Australian army.
 
Their roos have MANPAD SAMs these days, so I'd say that they were probably as well armed back then with equivalent weapons back then. :D

Seriously though logicstics would kill any Japanese invasion of Australia. I do remember an AH in a book that explored the idea - in that chapter they manage to get ashore, but not very far off the beach. Essentially what happens is their defeat in Australia subsitutes for their defeat in the Solomons.
 
The problem was Japan's army was greatly overstretched already, thus they concluded that an invasion of Australia was impractical and the best method was to isolate it. Could the Japanese have successfully invaded Australia? Yes, they had the naval and land assets to do so, but only if they pulled a significant amount of troops and ships away from their other areas, like China or south-east asia. In the long run this would have fatally overstretched the Japanese military and would have been a disaster, but yes if Japan had turned all its considerable resources to conquering and subjugating a lightly populated Australia defended by a distracted UK then it could have done so. In the end they likely would not have been able to hold Australia for long as once the Americans arrive in force they are totally screwed. Either way the OTL decision of the Japanese military to not invade was the right one, even if it was possible, Japan just didn't have the troops to properly pacify and defend all the land it already had, streching itself even thinner to invade Australia would have led to a much faster collapse of the Japanese Empire.

This is assuming that this invasion takes place probably before Pearl Harbour and particularly before Midway, otherwise an invasion will be a disaster.
 
This is assuming that this invasion takes place probably before Pearl Harbour...
Oh, you mean the time when all avalible sealift was devoted to the invasions of Malaya, the Philippines and the Dutch East Indies... places Japan actually needs to take so their industrial and military power doesn't grind to a halt in six months time due to oil and rubber shortages?
 
Oh, you mean the time when all avalible sealift was devoted to the invasions of Malaya, the Philippines and the Dutch East Indies... places Japan actually needs to take so their industrial and military power doesn't grind to a halt in six months time due to oil and rubber shortages?


Fair enough, with the US economic sanctions in place you cant really get rid of those other invasions since they were out of material necessity. I guess that would mean that Japan would pretty much have to abandon the China campaign and throw all its troops into a thrust south, culminating in an invasion of Australia.

I suppose the other window would be shortly after Pearl Harbour when the American Fleet is on the defensive and wouldn't be able to intervene at that time.
 
Invasions have an 'inner' logic: How fast can you build up the forces? Faster than the enemy opposing the invasion and you win, slower you lose.

It is of course important to get ashore, but then?

Brooke had it nailed when he asked Marshall: So we get ashore (Overlord that is). Do we go south, North? East or do we sit down and play (whatever that French railway game is called).

So Japan gets ashore and establish a perimeter.

If it is shortly after PH, US can of course hurl the carriers at it, but Japan is then sitting with six carriers and a very motivated set of pilots.

Submarines? it is a long way from Japan to Australia and those supply ships are not fast.

Enlighten me a bit on this as well.

Ivan
 

TFSmith121

Banned
Not that I'm disagreeing, but you're a little off

By the time invasion is possible Australia has the following Australian military formations are active and at home:

  • The 6th and 7th Divisions, both AIF, home from North Africa
  • Remains of the 8th Division, AIF, recuperating after heavy losses in Malaya
  • 1st Armoured, active since July 1941, achieved full OOB May 1942.
  • The 1st, 2nd, 3rd and 4th Divisions, Citizen Military Forces, active though with some sub-units deployed to New Guinea.
  • The 3rd Motorized/Cavalry (name depends on the exact date...), Citizen Military Forces, active.
  • The 2nd Armoured Division, Citizen Military Forces, forming
  • The 6th, 10th and 12th Divisions, Citizen Military Forces, forming.
  • Plus various other bits and pieces about the place.
So, just counting Australian troops, that's 6-9 infantry divisions depending on the exact date of the invasion; 2 armoured divisions and one motorized division. There also the possibility of bringing the 8th Division back from North Africa early.

In terms of American forces in Australia...

  • The 32nd Infantry Division arrived in April-May 1942.
  • The 6th Infantry Division arrived in April 1942.
So, that's 8-12 infantry divisions, 2 armoured divisions and one motorized division available.

Japanese sealift means they're hard pressed to bring more than 3 or, if really stretching things, 4 divisions to the game.

Yeah, unless the Japanese land in the Middle of Nowhere, NT/Far North Queensland the landing goes squish quickly. If they do land Middle of Nowhere, well, it's a self supporting PoW camp until supplies run out, thereafter the landing ceases to be a problem... unless the Salt Water Crocs get 'em first.
;)

Not that I'm disagreeing, but you're a little off on the OOB.

The US 6th Infantry Division did not arrive in the Southwest Pacific Theater until January, 1944.

In 1942, US divisions that reached Australia included:
  • Americal Infantry Division - 26 Feb. 1942 (as TF 6814, POPPY Force; hq and two RCTs; third RCT arrived 7 April); re-deployed to New Caledonia 6 March 1942;
  • 41st Infantry Division - 6 April to 13 May 1942 (hq and three RCTs)
  • 32nd Infantry Division - 14 May 1942 (he and three RCTs)
The pre-war AMF order of battle was 1-4th Infantry and 1 and 2nd Cavalry divisions, plus various separate brigades and battalions; the 5th Infantry Division was organized from separate brigades in 1941-42. The AIF forces in Australia in 1942 included the 6th and 7th Infantry (which arrived in the spring) and the 1st Armoured, which was converted (as you indicate) from a training division to a field division in 1942. The 8th Division was destroyed in Malaya; one brigade headquarters, the 23rd (IIRC) had remained in Australia, but its three AIF battalions were lost in the NEI, Timor, and New Britain, so the brigade was re-built with AMF units. There were multiple field, coast, and AA artillery units (including US Army) as well as engineers (including US Army) in Australia and New Guinea in 1942, and various separate brigades/brigade groups/fortress units/training units with home defense roles, etc.

One issue to keep in mind is that the AMF order of battle generally amounted to a cadre that required mobilization of the militia to get to anything approximating full strength; the total of AMF/AIF personnel in Australia in December, 1941 was something like 250,000 (although training varied widely; only about half of the AMF - 125,000 - had been in service for as long as six months, for example); there were another 50,000 Volunteer Defense Corps (Home Guard equivalent), including many WW I veterans.

The above does not include the RAN and RAAF, or the AIF units outside of the Southwest Pacific, notably the 9th Division, which was in Africa and did not return home until very late in 1942.

Still, it comes down to (at least) 300,000 Australian soldiers and VDC, the RAN and RAAF, and (at times) 2-3 divisions of US Army, various supporting elements, and both the USN's Southwest Pacific Force and the USAAF's units that became the 5th Air Force.

Bottom line, between the distances involved (both within Australia and from any likely Japanese forward bases, much less the Home Islands) and the Australian and American forces in the theater, plus the reality of the overstretch of the IJA, IJN, and Japanese merchant marine that were evident in 1942, there's really no rational strategy for a Japanese invasion of Australia the continent.

It's as unlikely to succeed as a Japanese invasion of Hawaii or India.

Best,
 
Their roos have MANPAD SAMs these days, so I'd say that they were probably as well armed back then with equivalent weapons back then. :D

Seriously though logicstics would kill any Japanese invasion of Australia. I do remember an AH in a book that explored the idea - in that chapter they manage to get ashore, but not very far off the beach. Essentially what happens is their defeat in Australia subsitutes for their defeat in the Solomons.

Don't forget about the Drop Bears - very dangerous
 
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