There are two components to this why CMs have an issue with it. So I will address the one that finally convinced me that some clarification needed to be made.
I don't generally have a problem with Dogpile or swarm attacks. Why? Because yes, the defense force at the first target is out numbered but remember that the attackers are burning fuel at their full rate, probably using up their WEP, using up ammo, possibly losing alt, and becoming disorganized / less cohesive than they were before the engagement. Resulting in the fact that they are less capable of effective combat at the second target. The defense force there will have an easier time of things because they have not used their WEP up, they have no used their ammo, they have not taken damage, etc.
Of course it sucks for the first group of defenders. And yes, an engaged CiC who is actively watching the whole battle and coordinating all of his forces can definitely compensate to an extent in the face of these attacks. I can detach part of a nearby defense force and send it to help. Of course he has to make a decision that because of the size of the attack force that it has been tasked to hit to areas and that the defenders he are rushing in are from the attack forces next target. That is a hard thing to know and is the risk any CiC runs when making battlefield decisions. All part of the game.
However, the defender is still at a bit of a disadvantage here because he has to defend all his targets. He can't really decide to abandon one before it is attacked. So the best he can really do is send some of the defenders from point A to point B. Also remember in most designs CMs try to place targets 50 miles apart (2 sectors). What does this mean? It means that most defending squads take up defensive positions between what they are defending and where they expect an attack would come from but also in a position to react quickly to an attack from an unexpected corner.
Now lets say a whole squad leaves and goes to help another defense force 50 miles away. At a speed of 300mph it will take them 10 minutes to get there. Now lets say the enemy is actually picked up farther out so that the original defending force picks them, falls back and calls for help. Depending on where they pick them up the help would probably arrive either say 10 - 15 miles forward of the base being attacked or over the base being attacked.
So they are 10 - 13 minute now out of position for depending their own base. The time back can be even greater depending on what time period, plane set, and the fact that the defenders could have given up alt and or energy (they are low and slow). Meaning they are gambling heavily that the attack they are helping to defend against is targeting them next and their is not a separate attack on the way to their base.
I would say that the defender is at a disadvantage since his forces are chained to defense targets and can't completely abandon them. But there are still things he can do (send in reinforcements from two bases in distance, resulting in only weaking those two areas slightly .. send in 2 planes from 2 bases for a total of 4 more pilots can help .. or 3 and 3 for 6 more pilots).
So a dogpile or swarm attack can be mitigated to some extent by the defending CiC's actions but do realize that the defending force is limited to an extent, per above.
Now where I convinced this was an issue was not by the swarming attack but by the follow on portion. Simply put a follow on attack only guarantees an attempted attack at the first target. As stated the issue that final caused all this about happened in the July FSO. Here is the map from the frame that final caused the CMs to decide that clarification of the credible attack rules as needed.
As you see there is plenty of distance between two targets, they were not placed to close together. Also you will see that there were much closer launch bases to some targets so routes that had to traverse 10+ sectors were unnecessary.
Here are the orders for one of the strike groups:
follow white line at 3000ft.Target 1 and 2. hit one and rearm at 29 if needed,if you have load left proceed to 2
you get a second life in plane of choice so if your targets are dead up a a6m loaded and regroup as defense or watch for text of valid targets,otherwise regroup and keep hitting your targets
The CiC in this case, also in cases previous to July, did not understand that target 2 was not optional. It had to be attacked in the T+60 window. Also it is just common sense, or we assumed it was, that an attack plan would be constructed that would enable an attack force to hit a target within the T+60 window. As said this was the latest example that were wrong on that account.
Even if things went fine again you are stuck in a position where the attack on target 2 might not happen. Since they are going into battle at target 1 and could be destroyed, use all their ordinance there, etc., etc. What does this means? It means as a judge I can't say that a credible attack was done on 2. I can't judge that attack was attempted on 2 since the force was instructed to attack one and then continue on. They could be stopped cold 50 miles away from target 2. Does this count as being intercepted or does not .. after all they actively attacked a target. They were not intercepted going to target 2.
In my opinion this is what concerns me more than the concentration of forces. A follow on attack does not guarantee an attack on a the second target no matter what a CiC instructs to his troops. It also muddies the picture to an extent that for the second target all you can go by is whether the target 2 took damage or not? Then of course you are stuck with the question how much damage? Is it a credible attack if the bundled attack force spend all their ordinance at target 1 except for maybe 10%? Is it a valid attack on target 2 if only 1 bomber or 1 formation holds back bombs from hitting target 1 to attack target 2? How do CMs know how much ordinance is reserved for each target? Realistically we can only tell by bomb hits so lets say the attack force kept back 30% of their bomb load to hit target 2 but completely missed (remember in BoB frame 1 the LW bomb effectiveness was like 30% overall .. so it can happen). So if they miss how does the CM know if they just missed or if say instead they ran out of bombs at frame 1 or only let loose maybe 1 bombers worth of bombs?
On a non follow through attack I can tell from a CiCs orders what was assigned and intended. Force A with an escort squad of Y and a bomber squad Z was tasked to hit target 1. If they miss I still know they were carrying xxxx amount of ordinance soley intended for target 1. If they got intercepted I can go they were intercepted and destroyed while trying to get to target. Follow on attacks muddy the picture to much for me to make anything but Draconian calls on target 2.
Can we compensate for this via design? To some extent yes. If targets are within 25 miles of each other we can and I believe have (will have to dig up some of my old designs) designate both fields as a single target .. allowing for the bundling of attacks and defenders. However, when bases are spread out farther than that we run into the disadvantage issue to the defender (which they can partially compensate for) but then have issues determine and judging an attack on target 2.
If you increase things to 75 miles the issue remains. If you increase to 100 miles then you start to have an issue of flight times where after the attack on the target the defenders might as well land since it is a 20 minute flight to the next defensive target. Meaning they say engage in battle at T+50, by T+60 things are done, refueled and reup say by T+70, now it would take them to T+90 to get to another base to help with the defense, probably longer since they have to add in time to get to altitude (assuming they were flying at 300 mph the whole time). So you start to see that at 100 mile spread between bases it basically means defend your target and when the fight is done basically you don't have time for anything else.
This is why we usually go with around 50 miles between bases and have done so for many, many, many FSOs.
The other issue is of course that now a dedicated attack was not in place for 2. Just hit 1 and continue onto 2 but quite a few things might develop during the battle that prevents this. Meaning that defenders at 2 might end up flying 120 minutes and have no action. People tend to get upset over this and we CMs do get email over it on a fairly consistent basis. When we can say, hey an attack was planned but your allied squads stopped it they accept that and understand these things happen.
When you get one force of defenders swarmed and a second group flying with no action at all you start to see where the problem is. As stated this is not because of an isolate event or anything from just one FSO. This discussion about multiple incidents has been going on probably for over a year now with us finally agreeing we need to clarify things in July.
Then do to a web update mixup one page was updated but the other was not.