So I have been trying to wrap my head around interdiction.
The rule book is a tad vague as to the mechanics.
I suspect that the way it works is...every time a unit moves a hex, a die roll is made. This is compared to the value in the Parameter data...say 45%. I imagine that this is for a unit at full road movement stacking...say 350 guys.
It is then adjusted somehow for units that are larger/smaller then this as I notice through experience that small units are hit far less then big units.
I guess that its prorated, so a unit at 700 would be double 45% and a unit at 175 would be 22.5%
If the die roll is a success, the game then picks a random available? /all? aircraft from the other side's list and launches an attack with it. The value of that attack is multiplied by the Parameter data interdiction effect. Say 20%. The defending unit gets no protection and is in travel mode.
So for a game like Normandy..where the units are moving from the bottom of the map up...travel about 100 hexes to reach the front line. A small unit of 4 guns will be hit (40/350)*45 = about 5 times. A single gun will be hit about once.
Note that speed doesn't matter...it just means more checks per turn since every hex is evaluated as the unit moves.
That is my understanding of it anyways...I could be wrong.
I also notice that when visibility is lower, interdiction seems to hit less. So it probably multiplies in the chances as well..probably the parameter data for Air Limitation: say 10% at 2 visibility, 25% at 3, 50% at 4 and 100% at 5...
....so the chance to get hit when visibility is 3 would be 45% * 25% or 11.25%.
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Hmm..I read also that probability is modified by terrain modifiers....but since units are usually moving along a road....I assume that it would be no modifier. Otherwise, it would be multiplied by the defence of the terrain...say 50% for bocage.
For fun, I set up a PDT file where interdiction was upped to 100%. I made all road movement cost 1.
Moving 600 man battalions (with road stacking at 350), I was hit rarely. I noticed that visibility was 2 and that 10% was the air value at that visibility.
I changed all visibility air effects to 100%.
Now my 600 man battalions were being hit in each and every clear hex they moved in..along the road. Occasionally they would avoid interdiction in a terrain hex if the road hex passed through it.
I tried moving smaller units. 120 man units could run a ways along the road without being hit...it seemed to be less then 1/3rd of the time, but I didn't do enough for a proper value. Definitely less though.
I then changed the stacking limit to 3500 road, and 15000 normal. (just added a zero to the end). Now interdiction was rare. The 600 man battalions could run along the road and get hit maybe once. (for 10 hexes movement)
Note that it didn't seem to matter...moving for 6 in the open or 1 along the road seemed to have the same percentage.
Yet another observation:
I took all aircraft out of the scenario..but kept the interdiction values.
No interdiction occurred.
I added one flight. The usual air interdiction happened....I used that air flight...and the next turn, the usual air interdiction occurred..
That means that the air is chosen from all air, not available air. I could dig deeper to see if it picks air that is reinforcement, or so on...but I think I got the gist.
Ginger, Biggles and Braddock love shouting Tally-Ho just when one unit passes thro another.
Remember this ain't always AFV's gett'in hit, it's a lotta horse transport, trucks, all manner of towed guns and many marching infantry units. I.E. soft targets.
That's why the game has AAA units, of course some people deploy them in the frontline or in large unrealistic stacks behind a mass of armour.
Not that I played many boardgames but they had interdiction tables which give the same effect.
It does factor in the terrain you are passing threw, you will be alot more likely to have interdiction going threw clear terrain then you will going threw a city hex. From what i know if the terrain mod of a city is -40% then youll have 40% less chance of getting hit going threw the city hex than you will a clear hex.
As units move on the map in Travel or Rail Mode, there is a chance that their
movement will be Interdicted by enemy air units. This probability is based on
Parameter data per side (see the Parameter Data Dialog in the Main Program).
The probability is based on the total number of units in Travel or Rail Mode in
the hex being moved into. The probability is modified by any terrain modifier of
the hex being moved into. The probability is half during Dawn and Dusk turns.
If Interdiction occurs, then an Air Strike occurs against a unit in the target hex
using an air unit that is representative of the type of air unit available to the
enemy side. However, this air strike does not count against the air units
available by the enemy. Note in addition, that movement by units in Deployed
Mode into hexes occupied by units in Travel or Rail Mode can also trigger an
interdiction attack against the units in Travel or Rail Mode.
In addition as long as you have AC available on that turn interdiction will happen as normal weather its 1 AC available or 100.
Aaron
I am making no judgement on the why's of interdiction..only trying to come to grips with the mechanics..
To sum up what I have discovered so far:
The percentage chance of interdiction is modified by:
Visibility.
Terrain in hex.
Size of Unit.
Interdiction Percentage in parameter data.
The amount of damage you take is modified by:
Visibility.
Aircraft in Scenario OOB.
Interdiction Effect in parameter data.
What doesn't effect interdiction is:
Anti-aircraft.
Movement cost.
Used Aircraft.
So in Normandy (for example), the slow road through the Bocage to the front line is a safer route to take, then the main highway that passes through the open.
It is better to have your units walk one hex a turn deployed then to move in travel mode when visibility 5. Its a huge benefit to waiting until lower visibilities.
There is no Dawn/Dusk in Normandy.
The Game has AA units to protect on map assets, and is best used in large bunches to protect masses of armour...and will do absolutely nothing if you spread it around in a futile attempt to prevent interdiction.
I don't have the Zetterling Normandy book however we have the net.
The III Flak Korps suffered greater casualties than most units marching to the front but still managed to shoot down 35 aircraft !!!.
Was deployed from Falaise to Le Beny Bocage, which is the main route to the landings.
Later it was deployed WELL BEHIND THE FRONT LINE where the 88mm guns were used as ARTILLERY.
Everyone is different we are all unique so we have different gaming expectations.
I have always wished FlaK had some effect on interdiction, which it does not.
See the Bulge '44 Dark Winter scenario for 88 FlaK guns depicted as indirect fire arty, not super AT.
Yes...if I wanted history, I would read a book. If I want to be a General, I will command forces. Although I do enjoy playing against book readers....they are usually quite predictable, and I like the way they whine when their history lesson fails to win them their inevitable victory.