Alternate Defense of Guam 1941

While the Washington Naval Treaty had prohibited the fortifying of Guam and th Japanese controlled Marinas Islands there appeared to be a loophole as it allowed fortifications and coastal guns that were there to remain there. Thus up until 1930 the US had 8x 6Inch M1900 coastal defense guns, 4x 7 inch USMC Coastal defense guns and 4x 3"/23 caliber dual purpose guns. The 6 inch guns had a range of 17,000 yards, 7' guns 15,000 yard and the 3 inch guns could fire out to 14,500 yards.
All of these weapons were fully operational up to the time that they were ordered removed by the Hoover Administration in 1930.

So if the Hoover Administration instead did not order them to be removed they would still be there in 1941. Thus the only thing that would be needed would be to maintain a larger force of Marines and Naval Personnel to Man them.
Prior to the Invasion the Insular Guard on Guam had been expanded.
The amount of small arms included 15 BARs, 30 Lewis guns and 260 Springfield Rifles. There were also a few LMGs.
It is most likely with rising tensions that the garrison might have been brought to a full wartime level meaning all guns being manned and perhaps a Marine Defense Battalion .
The question of whether Guam could have held out is a good one. The Japanese attacked the island in 1941 with over 6,500 troops but there was no coastal defense guns . If they had been there and the Marine-Insular Guard force strengthen then perhaps the invasion could have been repelled at least the first and perhaps the second attempt.

The assumption will be that the Hoover Administration did not remove the coastal defense guns and the 3 inch dual purpose guns from Guam but for a period of time the Military garrison on the island was reduced. For most of the first term of FDR the island of Guam remained a backwater. Pan American airway did use the island as a seaplane base and stop on the route to Asia.
But with FDR's re-election in 1936 attention began to shift from the Great Depression at home to the rising problem of aggression by Japan , Germany and Italy. Douglas MacArthur retired as US Army Chief of Staff and was hired by the Government of the Commonwealth of the Philippines to begin training and expanded Filipino Military for eventual Independence, which was hopefully take place in 1942.
Yet it wasn't until 1938 after the outbreak of hostilities between Japan and China that the US began to look at the defense needs of its territories in view of the rising prospects of a war between the US and Japan. To that end additional Marines and Naval personnel were sent to the islands. The coastal defense guns which had not seen service since 1930 were once again checked and tested. Maintenance work was approved but in view of a tight budget not a lot of money was available to get things running. In 1939 tensions finally woke up the doubters in the Roosevelt Administration that War was likely. When it actually came in September of 1939 it was a shock.
No one believed that the war would be long. The Invasion of Poland and its occupation by Nazi Germany the the USSR was stunning. news out of China about the violent clashes between the Republic of China and Imperial Japan made headlines. Shanghai, Nanking and the massacres that happen put the US on the road to a future clash with Japan. The US started to apply economic pressure.
At the same time President Roosevelt prepared to push for a two Ocean navy. Into this the President read a report about the guns on Guam and ordered that they be activated and the fortification that existed put in working order. Navy and Marine personnel were sent as well as civilian Construction personnel.

See the Pacific War Redux timeline and make a logical continuation if possible. The effects are the same, except that Guam is probably indefensible.

Even if the guns hadn't been taken down, it still doesn't change the balance of power in the Marianas that much. Those guns are all awful old...

CalBear's Pacific War Redux had it right when it had Congress decide to prepare for war like it was yesterday. That's what you're going to need to have any chance of the USN/USMC reinforcing Guam. There are too many other places with more strategic value that needed reinforcing first. In order to get Guam reinforced even a bit you're going to need the tide to rise and lift all boats proportionate to their strategic value and likelihood of success.

Without a navy to support Guam, and without modern weapons to sustain a defense, it would be a trap, just like the Phillipines, where numbers would mean almost nothing.

Coastal defense guns, without a vibrant airfield with modern planes, would mean little in the grand scheme of things. It might mean that one attack would be repelled, maybe two, but likely not long enough to mean a big difference unless the Navy made a big time effort to relieve Guam.

Look at the Japanese airfields on the Mariana Islands and you will realize why this is impossible. Holding the Philippines, Wake Island, Singapore, an Indonesian island or two [that is worthy of defence] and Burma will be more plausible.

All too true the defense of Guam would require a lot of effort and a major expansion of the forces available in the Pacific. Still I may give it a try and just see what I could come up with. By the Way there was a new version of the 7 inch gun that was developed so there was the possibility that they could have been replaced.
In 1939 the US Navy decided after being pressed by the President to build an Naval Air Field on Guam. New 7 inch guns were being sent to the island but the question was where to come up with newer 6 inch guns. There was a lot of demand for coastal defense works and Wake and Midway had priority in receiving them. The Marine defense Battalions were receiving the 5"/51 guns from Battleships that were undergoing modernization and in some cases these were guns from older Battleships such as the Utah. The Navy could send some more of the 3"/23 caliber guns to Guam perhaps increasing the number there to 12. Still it was a race against time.
Fortifications were improved that existed and the amount of personnel and weapons increased.
The Secretary of the Navy reported to the President on the progress of the work on Guam and continued to point out that in view of the Japanese bases located nearby the chances of holding the island were slim. It would be better to strengthen US bases elsewhere but the President ordered work to continue.
An airfield finally became operation in 1940 and the USS Lexington flew off 6 Wildcat fighters in June of 1940. The US Navy had nearly 400 personnel on the island and the USMC had nearly 500 Marines stationed there.

Fearless Leader said:

Even if the guns hadn't been taken down, it still doesn't change the balance of power in the Marianas that much. Those guns are all awful old...

CalBear's Pacific War Redux had it right when it had Congress decide to prepare for war like it was yesterday. That's what you're going to need to have any chance of the USN/USMC reinforcing Guam. There are too many other places with more strategic value that needed reinforcing first. In order to get Guam reinforced even a bit you're going to need the tide to rise and lift all boats proportionate to their strategic value and likelihood of success.

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Agreed. Calbear's timeline is the most plausible defense scenario for Guam that we've had. Airpower will be essential to saving the island - and other WestPac assets as well.

A couple of things

On its own its useless.

As part of an upgrade for Midway and Wake as well as more assets and effort expended prewar in the Phillipines then yes it makes sense.

Also IIRC - there was an agreement in the WNT I and II not to upgrade certain naval bases / bases etc and I would think that this would fall under that.

A much larger garrison would be required (Brigade+) as well as greatly improved air power which would involve upgrading the runway including revetments etc.

The Loophole in the Washington Naval Arms treaty would seem to be that the treaty did not require the disarming of Guam only that larger or additional guns could not be added to it. Thus the US could replace guns that were obsolete with newer ones of the same size and number without violating the treaty. It was also clear that after the Collapse of the London Treaty talks that all bets were off and that the US or any other nation could arm with whatever weapons they wanted wherever they wanted,
However, I would agree that to realistically stand a chance Guam would need a lot more defensive forces. A brigade sounds about right but even if the President pushed for it the Marine Corp was too small to send a Brigade to Guam. Perhaps a reinforced Marine Defense Battalion and further expansion of the Insular Guards.
If Wake was allowed to complete its build up things might have been different.
The destruction at Pearl Harbor gave the Japanese an advantage for a time.

The rebuilding of the Islands defenses had actually started(in TTL) back in 1938 with some restoration work that included a survey for an air field. The Munich Crisis had showed the President that a war in Europe was likely and the country's defenses needed rebuilding. The President moved to push the 2 Ocean Navy through the Congress. Stating that the country needed it and it would stimulate the economy.
The Bill narrowly passes the Congress. The President is determined to send a signal to Japan to stop its aggression. Older guns on Guam are being replaced and the Airfield is build. The President pushes to increase America's Marine Corp, Navy and Army.
In 1939 the Navy and Marine Garrison is increased but its a slow step forward. Work was also being done on Wake and Midway.

2 Ocean Navy Bill or a 20% bill?

chris N said:

The rebuilding of the Islands defenses had actually started(in TTL) back in 1938 with some restoration work that included a survey for an air field. The Munich Crisis had showed the President that a war in Europe was likely and the country's defenses needed rebuilding. The President moved to push the 2 Ocean Navy through the Congress. Stating that the country needed it and it would stimulate the economy.
The Bill narrowly passes the Congress. The President is determined to send a signal to Japan to stop its aggression. Older guns on Guam are being replaced and the Airfield is build. The President pushes to increase America's Marine Corp, Navy and Army.
In 1939 the Navy and Marine Garrison is increased but its a slow step forward. Work was also being done on Wake and Midway.

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What is in the 2 Ocean Navy Bill of 1938? Is it a near replication of the 1940 bill (Essex, Iowa, Montana, Alaska, Baltimore, Cleveland cookie cutter assembly lines) or is it a 10% to 20% increase in fleet strength bill (1 or 2 carriers (maybe Hornet and Wasp as modified Yorktowns), an additional North Carolina and an additional South Dakota, 4 more cruisers and 30 destroyers)

The 2 Ocean Navy Bill of 1938 would be bringing the Bill forward 2 years that was passed in 1940 in OTL. I would expect that with the outbreak of the war in Europe that additions to the Naval Bill would be made in January 1940. Thus additional ships would be ordered. Thus the USS North Carolina and USS Washington would join the fleet much earlier as would the USS Essex and the USS South Dakota might very well be the third North Carolina class Battle ship. In addition the Navy would order another 40 destroyers. Expect a Four additional Brooklyn class light cruisers and the start of the Cleveland class earlier as well as the Baltimore Class arriving in 1942.

By 1940 the War in Europe had fully broken out. It would be just a few months before the Germans would strike Denmark and Norway. Then in May the war would begin in earnest. France and Britain were already buying plans and equipment from the US, This was increasing US production capacity.
The US Military was recruiting more but there was still not enough influx of manpower to fill all of the needs.
Guam and Wax were seeing lots of Construction as was Midway. Admiral Husband E Kimmel had replaced the departing Admiral Richardson. The old Commander in Chief warned his successor that he need more of everything and to be on guard. Japan was a problem that would grow.

All of the & inch guns had been replaced on Guam and most of the 6 inch guns were being replaced. The island now had 18 3 inch /23 DP guns and the number of Wild cats had finally risen to 15. There were some PBYs. The number of Marines on the island had finally risen to 920 and the Nay had another 500 personnel. The Insular Guard was up to 250 men and there were another 100 undergoing training. The Marine Commander was requesting at least another 500-900 men and could use more than 3 times that amount. At least he now had some 30 caliber and 50 caliber Machine guns and some 60 and 81mm mortars. He had turned some vehicles into makeshift armored vehicles and had equipped then with several Lewis LMGs.

chris N said:

By 1940 the War in Europe had fully broken out. It would be just a few months before the Germans would strike Denmark and Norway. Then in May the war would begin in earnest. France and Britain were already buying plans and equipment from the US, This was increasing US production capacity.
The US Military was recruiting more but there was still not enough influx of manpower to fill all of the needs.
Guam and Wax were seeing lots of Construction as was Midway. Admiral Husband E Kimmel had replaced the departing Admiral Richardson. The old Commander in Chief warned his successor that he need more of everything and to be on guard. Japan was a problem that would grow.

All of the & inch guns had been replaced on Guam and most of the 6 inch guns were being replaced. The island now had 18 3 inch /23 DP guns and the number of Wild cats had finally risen to 15. There were some PBYs. The number of Marines on the island had finally risen to 920 and the Nay had another 500 personnel. The Insular Guard was up to 250 men and there were another 100 undergoing training. The Marine Commander was requesting at least another 500-900 men and could use more than 3 times that amount. At least he now had some 30 caliber and 50 caliber Machine guns and some 60 and 81mm mortars. He had turned some vehicles into makeshift armored vehicles and had equipped then with several Lewis LMGs.

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I think its unlikely that F4s would be available in 1940 or even 1941

I would expect Brewster F2A if USN/USMC or P36s if USAAF

Cryhavoc101 said:

I think its unlikely that F4s would be available in 1940 or even 1941

I would expect Brewster F2A if USN/USMC or P36s if USAAF

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Agreed, you would probably see a squadron of Marine F2As and maybe a squadron of USAAF P-36 or even P-35s. The Marines might even still be operating old F3Fs.

You might see a USMC scout bomber squadron there as well. Probably equipped with a mix of the old SBC-4s and SB2Us but maybe if you are lucky the first mark SBD-1s (the ones the Marines got - no self sealing fuel tanks, .30s not .50s in the cowling, and a smaller fuel load).

Let me state once again that the Navy Bill that in OTL was passed in 1940 was passed 2 years earlier in this time line. That would possibly mean that some aircraft were available earlier. The F-4 Wildcat was delivered to Wake Island in 1941. So it is possible that the Wildcat would also be available then or even in late 1940.
However, the following changes will be made to the air group on Guam: In 1940 the USMC sent 12 Brewster Buffalo s to the island . They were joined by 6 of the new Douglas SBD-1 Scout/Dive Bombers. As you mentioned these are the earlier aircraft and lack the modification. In December of 1940 the Lexington launched 6 F-4 Wildcats which joined the air group. Further aircraft were promised for the Spring and fall of 1941.
The demand for fighters precluded the USAAF from snding the P-36 to Guam as MacArthur was asking for more fighters for the Philippines including the new P-40.

chris N said:

Let me state once again that the Navy Bill that in OTL was passed in 1940 was passed 2 years earlier in this time line. That would possibly mean that some aircraft were available earlier. The F-4 Wildcat was delivered to Wake Island in 1941. So it is possible that the Wildcat would also be available then or even in late 1940.
However, the following changes will be made to the air group on Guam: In 1940 the USMC sent 12 Brewster Buffalo s to the island . They were joined by 6 of the new Douglas SBD-1 Scout/Dive Bombers. As you mentioned these are the earlier aircraft and lack the modification. In December of 1940 the Lexington launched 6 F-4 Wildcats which joined the air group. Further aircraft were promised for the Spring and fall of 1941.
The demand for fighters precluded the USAAF from snding the P-36 to Guam as MacArthur was asking for more fighters for the Philippines including the new P-40.

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In 1939/40 the Navy picked the F2 Buffalo over the Wildcat due to its then better performance. To be fair in 1939/40 its probably good enough to match the Japanese Navys Fighter plane of the day - the A5M

The A6m was a shock to everyone!

Of course during 1941 the Wildcat improved and became the better aircraft - but if you want to "Keep this TL Real" then the Aircraft used in 1941 would have been those in service in 1939/40.

And that is the F2 and P36 where fighter planes are concerned.

Perhaps mention that demand was outstripping supply and while the squadron was due to be equipped with F4s this was unlikely to start happening before X date

As an aside whats the distances beetween Hawaii, Midway, Wake, Guam and the Phillipines - reason for asking could aircraft by island hopping self deploy as far as the Phillipines?

The Only aircraft that I recall having flown to the Philippines was the American B-17 Bomber. It flew from the west Coast to Hawaii and then refueled and after a days rest the crews flew to Wake where they again refueled. Then it was directly on to the Philippines. Remember in Our Time Line there was no airfield in Guam but there was a seaplane base and a stop by Pan American. I will have to check but it might be possible to fly from Wake to Guam with the USN aircraft. I doubt if aircraft such as the P-36 could reach but the P-38 could.

Okay lets say that the F-4 Wildcats were not sent to Guam until the late Spring of 1941 ( June) and instead additional Buffaloes arrived. In The early Spring of 1941 at the Request of the President additional Marine forces were dispatched to the island. They arrived in April 1941 bringing the Marine force to 1,900 Marines Manning the Coastal defense guns and providing Infantry support, There were an additional 200 marines that Manned the Squadrons and provided Maintenance and AA crew. More reinforcements would arrive in June and a final reinforcement in October 1941.

The Improved version of the Brewster Buffalo could have flown the 1506miles from Wake to Guam but the Dauntless would have to have been delivered either by carrier of by Cargo ship as it lacked the range to reach the island.
Distance of Wake to Peal was 2303 miles. Basically aircraft with the exception of the B-17 would have to be delivered by either Carrier or Cargo ship. All USN/USMC aircraft could be flown off carriers and the USN delivered the P-40 to Malta by carrier in WWII. Of course the B-25 was capable of being launched on a 1 way trip from a carrier as Col Jimmy Doolittle proved.