Operation Olympic

[Telumar]

Be sure to read section 19.6 in the manual, ending with this:

"Both of these formulae pose a tactic for the
phasing player: bring the entire fleet to be moved
through the interdictor’s range into its detection
before moving through. The more in-range targets
detected the less interdiction there will be per
individual move."

This is moot because, in this scenario, a battery of 150mm coast guns seems to be able to duke it out quite happily with a battle group. As implemented, the coast gun reaction mechanic requires coast guns to be broken out to a separate unit in every scenario otherwise the infantry in the unit will soak up the phasing player's fire, giving the coast guns a huge advantage.

From 19.6:

"Chance of surface interdiction per in-range surface
interdictor:

Target Value of Moving Unit or Stack / Target Value of
all detected in-range Units.

Note that if the moving stack is the only one detected,
then the chance of interdiction is 100%. Also, if
there are 100 friendly ships and 100 enemy ships in
spotting range, the chance of interdiction will be 1%
per ship, averaging 1 interdiction per moving enemy
ship – it pairs off both side’s ships (on average)."

So...if only one target is in range, it's automatically going to be interdicted. If it is one of dozens of targets in range, it has a chance to get through.

How would this work? I mean one unit has to be the first, this unit will take a hit in each case (as soon as it is detected). Then the player moves the next unit into range with a chance of 50% hit upon detection and then the third with 33% and so on..? It's not that they all move at the same time

Besides that: With three units having entered range the chance per unit to get hit is not 33% but 61% on average (100+50+33/3). Of course the per unit values are right upon first strike each but the average is not. If you restart to count once everyone is in range the numbers are as described, but not upon entering.

[Curtis Lemay]

How would this work? I mean one unit has to be the first, this unit will take a hit in each case (as soon as it is detected). Then the player moves the next unit into range with a chance of 50% hit upon detection and then the third with 33% and so on..? It's not that they all move at the same time

Besides that: With three units having entered range the chance per unit to get hit is not 33% but 61% on average (100+50+33/3). Of course the per unit values are right upon first strike each but the average is not. If you restart to count once everyone is in range the numbers are as described, but not upon entering.

1. Use a pre-dawn turn to move the entire fleet to just over 10km from the coast. When dawn occurs, the entire fleet is simultaneously revealed - without triggering any interdiction. (And sort of realistic).
2. If that isn't possible, move the fleet no closer than 25km from the coast. Any interdiction will be at huge range and minimal impact.
3. Move the most heavily armored units into range first.
4. Get all surface naval gunnery in range first, before any auxillaries or troop ships.
5. With all gunnery units in range, paste the coastal guns with them.
6. Continue like so till the gunnery units are at their optimum range.
7. Lastly, bring the troop ships into range and charge the beaches.
8. Contrast this with sending individual embarked units to the beach by themselves (one at a time). They will be eaten alive one-by-one.

[golden delicious]

So...if only one target is in range, it's automatically going to be interdicted. If it is one of dozens of targets in range, it has a chance to get through.

Bob 150mm guns shouldn't be damaging battleships

[golden delicious]

1. Use a pre-dawn turn to move the entire fleet to just over 10km from the coast.

When you're starting with the assumption that the game has sub-24 hour turns, there's a problem.

4. Get all surface naval gunnery in range first, before any auxillaries or troop ships.
5. With all gunnery units in range, paste the coastal guns with them.

Bob the coast guns win. Did you look at the scenario?

[Curtis Lemay]

So...if only one target is in range, it's automatically going to be interdicted. If it is one of dozens of targets in range, it has a chance to get through.

Bob 150mm guns shouldn't be damaging battleships

I assume they do because the NAD was 10 => ten salvos of fire per round before the invaders can respond. Of course that had to be fixed to NAD => 100 => 1 salvo per round each. That should have been done now.

[Curtis Lemay]

1. Use a pre-dawn turn to move the entire fleet to just over 10km from the coast.

When you're starting with the assumption that the game has sub-24 hour turns, there's a problem.

That wasn't an assumption as my point 2 should have made clear. This procedure wasn't specific to this scenario. I was just explaining how the rule I highlighted can benefit invaders. Even in this specific case, bringing the entire invasion fleet into view at max range will reduce the number of shots each invasion element must pass through.

4. Get all surface naval gunnery in range first, before any auxillaries or troop ships.
5. With all gunnery units in range, paste the coastal guns with them.

Bob the coast guns win. Did you look at the scenario?

Again, of course the coast guns need to be separated from other infantry. Perhaps including coast guns in Port Attacks would help? Or a specific attack that concentrates on coastal gunnery?

[sPzAbt653]

The NAD is set to 100 in the scenario I posted above. The US Navy starts just offshore at all three invasion beaches. I use the Navy to bombard enemy shore batteries for five rounds, and also use Heavy Bombers to do the same. After those five rounds I move the embarked units to the beaches, and they get plastered and any remnants that make it ashore are easily wiped out by the defenders in their turn [US staging areas have been put in supply for current testing]. Adding to the carnage is the issue of some embarked units not advancing into cleared beach hexes, leaving them at sea to take more hits during the enemy turn. I think that any embarked unit that participates in combat that results in a beach being cleared should advance into that hex. I think that shore batteries shouldn't need to be eliminated, they just need to be suppressed [according to history].

This scenario didn't work well in III and it doesn't work well in IV. Some modifications should be able to fix it.

[willprest]

I find this scenario very interesting and have been trying to get it to work.

The first thing I did was set the naval attrition divider to 90 as per this thread: https://forums.matrixgames.com/viewtopi ... 3#p5236113

I then moved each of the amphibious groups further away from the Japanese coast using the scenario editor. This means that things like destroyers are not destroyed immediately if they move or during the first Japanese turn.

I then spent several turns using the cruisers and battleships to batter the 150mm fixed guns, which are the most powerful anti-ship gun the Japanese have. These are in five gun batteries and normally include infantry and supporting arms as well. I have found that with a NAD of 90 they are not effective against heavy ships like cruisers and battleships but are very effective against the lighter destroyers. I took the heavy ships from the 3rd Amphibious group which is positioned to attack from the south and placed them with the 7th Amphibious group which is attacking from the east. This has been very effective at destroying the 150mm guns. I have found that you can take the heavy ships right up to the beach and they are able to survive while dealing out a lot of damage.

However, there are some challenges. Firstly, there are lots of 150mm guns spread over several hexes on the eastern beaches. Secondly, the presence of the infantry and supporting arms means they absorb some of the damage rather than just concentrating on the 150mm guns. I eventually got bored so decided to attempt a beach assault with three infantry regiments. I moved the heavy ships out to sea to meet them out of range then headed back to the beach. The infantry took heavy casualties from the remaining 150mm guns and some of the 8in guns and traditional artillery when I got close. I successfully attacked the beach and landed all three regiments ashore but in the next Japanese turn they were completely wiped out. The Japanese PO is extremely aggressive to say the least. Many of the beach hexes are now over stacked with Japanese forces and are easy pickings for the heavy ships. The PO is also attacking my heavy ships during the Japanese turn and I am dealing out lots of damage in return. I left the air assistant on and that has done a good job of destroying the Japanese air force. I did play one turn as the Japanese so that I could attempt a massive air attack against the heavy ships to the east but this failed and resulted in heavy casualties. In short, this scenario is not as unbalanced as it may first appear.

I have one particular issue with coastal artillery in that there is no respect for line of sight or arc of fire, so coastal artillery can fire over land based terrain at maximum range on any arc (the same issue applies in the Gallipoli scenario where Turkish guns on the eastern coast of the peninsula can fire over it to British and French ships out to the west). In terms of the strength of coastal artillery, it seems ok when the NAD is set correctly.

In summary, I think the main reason the infantry are getting slaughtered both on the way to the beach and after landing is that this is the likely historical outcome if Operation Olympic had gone ahead, if only a limited bombardment by sea and air had taken place beforehand. It would likely have needed a sustained air campaign over many months, with potentially weeks of sea bombardment to enable allied soldiers to step ashore with any certainty of being able to hold on. From a scenario perspective it really depends on how long you want to spend fighting the air and sea war.

[golden delicious]

In summary, I think the main reason the infantry are getting slaughtered both on the way to the beach and after landing is that this is the likely historical outcome if Operation Olympic had gone ahead, if only a limited bombardment by sea and air had taken place beforehand. It would likely have needed a sustained air campaign over many months, with potentially weeks of sea bombardment to enable allied soldiers to step ashore with any certainty of being able to hold on.

I don't think this is the case. For D-Day, there was no significant bombardment until the night before. My understanding is that German coastal artillery had no effect on the landings. Perhaps the Japanese had more extensive coastal emplacements- but given the resources available to the Allies for the invasion, I doubt there would have been any need to begin bombardment any earlier.

The problem is solved by splitting the guns out from the associated infantry. Then the guns will die promptly during reaction fire when the Allies move.

[willprest]

I split the coastal guns from the supporting infantry and it definitely made life easier. I was able to destroy all of them within 1-2 turns and then land the infantry without any coastal gun interdiction. The best tactic was just to roam up and down the shoreline with the heavy ships and every time the coastal guns interdicted them they had an opportunity to fire back. This was probably a better use of the tactical rounds than firing at the coastal guns through planned combat as the ships have so many movement points. It does however mean they expend their supply very quickly. I did not lose a ship but some of them where nearly sunk.

[rhinobones]

While assault troops approach the beaches this scenario seems to have evolved from a non-historical state (100% amphibious casualties) to an equally non-historical state (0% amphibious casualties). Realistically the landing should incur some level of damage. Maybe you can test a few alternatives:

1. Assume the shore bombardment has already been performed keeping heavy naval units inactive until turn 2. Reduce the number/lower the caliber of the shore batteries to lower hits/kills.
2. Keep the infantry component in the shore batteries but reduce their number until testing yields a reasonable reduction by naval bombardment.
3. Give the shore battery formations “Delay” orders. Simulate shore battery direct fire with temporary air units set on “Sea Interdiction”. Typically, sea interdictions tend to do damage but not sink transports like artillery does.

Regards

[willprest]

There are still plenty of casualties during the landing, but these are being caused during the beach assault rather than 10-20km off the beach by coastal artillery interdiction. Given the scale of the scenario at 5kn a hex this seems fairly realistic, as it is really only in the actual movement from the sea to the shore, at a 5km hex size, that amphibious casualties are likely to be incurred. During the beach assault itself there is plenty of Japanese supporting artillery in range and if you want to start the beach assault within 1-2 turns then you will not have an opportunity to destroy all the infantry and supporting arms that were formally part of the coastal artillery by naval bombardment.

[Lobster]

Wargame Design Studio has a couple of nice games of the invasion of Japan.

[sPzAbt653]

I split the coastal guns from the supporting infantry and it definitely made life easier.

While I agree with the logic behind this change, I also wonder if the Japanese Naval Guns cause such havoc on the invading naval force due to the Japanese batteries being equipped with the most deadly TOAW anti-shipping gun, the 150mm fixed gun. I think I would rather try changing this first, as I would guess that the actual Japanese coastal guns were naval guns removed from ships or standard field pieces. These types of guns were used by the Germans in Normandy to little effect.

Maybe one of the database guys will chime in with what they might think reasonable anti-shipping values for Japanese coast guns might be. I found some details here:
https://www.allworldwars.com/Photo-Inte ... t-III.html

[cathar1244]

I split the coastal guns from the supporting infantry and it definitely made life easier.

While I agree with the logic behind this change, I also wonder if the Japanese Naval Guns cause such havoc on the invading naval force due to the Japanese batteries being equipped with the most deadly TOAW anti-shipping gun, the 150mm fixed gun. I think I would rather try changing this first, as I would guess that the actual Japanese coastal guns were naval guns removed from ships or standard field pieces. These types of guns were used by the Germans in Normandy to little effect.

Maybe one of the database guys will chime in with what they might think reasonable anti-shipping values for Japanese coast guns might be. I found some details here:
https://www.allworldwars.com/Photo-Inte ... t-III.html

Thanks sPzAbt653.

I had previously documented four cases of how anti shipping values are generated (they are not in the equipment database). This fixed gun anti shipping rating is yet another case.

In the case of fixed guns:

The AP rating, as given in the equipment file, is divided by 8. That result is then rounded, and multiplied by 3.

Example. The German 150mm fixed gun is given an AP rating of 260 in the equipment db file. 260 divided by 8 is 32.5. This is rounded to 33. Multiply by 3 to obtain the anti shipping rating of 99.

So, to obtain a different anti shipping rating, what would have to be altered in the equipment db file is the AP rating for the fixed gun equipment.

As far as an AP value for the German 15cm SK C/28 gun used in coastal emplacements, a value of 120 in the equipment database file would be reasonable. This will give an anti shipping rating of 45. Japanese 150mm fixed guns would have a comparable rating.

[sPzAbt653]

Top notch evaluation Cathar 1944, thank you so much!

Therefore, which gun to use to replace the 150mm Fixed Guns in the OOB?

The Type 45 15 cm cannon - was a coastal defense and heavy artillery gun used by the Imperial Japanese Army during World War II. During the 1920s large numbers of naval guns were declared surplus and placed in storage. Due to the type 45's weight, limited numbers [80] and limited mobility, it saw only limited use outside of the Japanese home islands and against land targets.
[The original scenario contains [155] 150mm Fixed Guns, therefore the Type 45 is probably not the one represented].
Type 89 15 cm cannon - was the main gun of heavy artillery units. 150 were built. It saw service during the Nomonhan Incident, the Battle of Singapore, and during the invasion of the Philippines and Hong Kong.
[There is no mention of these guns being used for coastal defense.]
Type 3 (1914) 140-mm naval gun - the most common coast defense gun used by the Japanese.
[No amount of number built is given in the Wiki page. There are 8 140mm Fixed Guns in the original scenario. These have an anti-shipping value of 57. Perhaps these guns should be used to replace the 150mm Fixed Guns. Or perhaps a new equipment entry should be created for this Type 3 140mm].
https://en.wikipedia.org/wiki/14_cm/50_ ... _naval_gun

[cathar1244]

Could be Type 45s, along Type 7 15 cm guns that were also used for coastal defense. Wiki states the 45s were used in the home islands.

https://www.valka.cz/15-cm-delo-typ-7-t21000#79656

[sPzAbt653]

I made an eqp for these based on the standard TOAW 150mm gun. I changed the Anti-Personal to 960/120, and that gave them an anti-shipping rating of 21.

[cathar1244]

Not sure if you want them to be fixed guns.

Fixed gun has a different DF ( 10 versus 1 ) and anti shipping calculation.

For non fixed guns, the anti shipping rating is:

Square root of the (equipment file AP rating divided by 2).

960 / 2 = 480. Square root of 480 is 21.9, rounds down to 21.

[sPzAbt653]

Well, I've got that one [which is based on the non-fixed 150mm], and this one, which is based on the fixed 150mm:

JPG1.png (164.1 KiB) Viewed 323 times

Which one to use?