There is no direct answer, unfortunately.

**Value D6 1 2 3 **

% 16.7 33 50

**Value D8 1 2 3**

% 12.5 25 37.5

**OOB % Sub** D16.7 A33

**OOB % DD** AD33

Nearest OOB Sub attack is “3” or 37.5% (+ 4.2%)

Nearest OOB Sub defense is “1” or 12.5% (- 4.2%)

OOB Subs attack is same as DD, so “3” is better.

Subs defense should be half Destroyer attack value, but “1.5” does not exist.

However, if added together:

A3+D1= 4 pips on D8 or 50%.

Compared to OOB A2+D1= 3 pips on D6 or 50%.

So, overall what Submarine A3 D1 gains in offense, is lost on defense.

In a way, making it with similar combat pips compared to OOB sub.

Considering Sub A3 D2 is mostly increasing defense combat value of Sub units.

So it is much stronger than OOB Sub: attack +4.2% defense +8.3%, sum +12.5%.

While Destroyer is only better than OOB by 8% : attack +4.2%, defense +4.2%, sum 8.4%.

But now, if you consider that **Sub keeps its iconic Surprise strike always on** (increasing odds of survival by 1.5) in D8 system, here is the interesting thing you get:

**Submarine D8**

**Attack** 2 *first strike* 0.25*1.5 = 37.5%*

**Defense** 1 *first strike* 0.1251.5 = 18.75%

For comparison:

**Submarine D8** when no DD is present.

**Attack** 3 *first strike* 0.375*1.5 = 56.25%*

**Defense** 2 *first strike* 0.251.5 = 37.5%

**OOB Submarine D6**

**Attack** 2 *first strike* 0.33*1.5 = 50%*

**Defense** 1 *first strike* 0.1671.5 = 25.05%

**Submarine D8**

**Attack** 2 = 25%

**Defense** 1 =12.5%

So, the first 8s dice Sub surprise attack @2 remains exactly as Destroyer “3” (37.5%) or Sub “3” when DD is present. And Sub’s defense 18.75% is near OOB 16.7% (by 2.05% margin).

In addition, this Sub A2fs D1fs preserved the 2:1 offense/defense ratio of OOB sub and similar odds.

On the opposite, Sub A2 D1 has 3 pips for 37.5% (is -12.5%) compared to 4 pips of A3 D1 and overall OOB Sub (50%).

While Sub A2fs D1fs get odds around 56.25% and overall is only 6.25% above OOB.

A3 D1 in first strike mode is 56.25+18.75= 75% and this is 18.75% above Sub A2fs D1fs.

That’s why IMO **the nearest combat values translation in D8 system is this Sub with Surprise strike always on.**

This surprise strike always on also increase Sub survivability (since enemy’s casualties cannot retaliate) does not make its surprise attack devastating as @3 Subs; which would be: 37.5*1.5= 56.25% which is also 6.25% above OOB surprise attack odds at 50% (33%*1.5). So this is aiming at increasing Battle of Atlantic feel.

This may also satisfy Wittmann (needs to nerf Sub) because Sub’s best attack never exceed 37.5%, which is far below OOB 50%. And never exceed 18.75% as best defense, which is also below OOB 25% for @1 first strike.

Total nerfing: 12.5 + 6.25 = - 18.75% compared to OOB Sub able to do Surprise strike.

But compared to OOB Sub regular shot : 4.2 + 2.05 = +6.25% better but below Destroyer increase of +8.4% odds to hit.

Destroyer can still be used as blocker against Stealth move and Submerge.

DD is also mandatory to allow aircrafts to hit Subs.

And on personal taste for better depicting strength of unit, I rather like that Destroyer have a higher direct combat value compared to Subs:

**Destroyer D8**

**Attack** 3 37.5%

**Defense** 3 37.5%

**Cost** 8

**Submarine D8**

**Attack** 2 *first strike* (37.5%) you get a hit 25% of time

**Defense** 1 *first strike* (18.75%) get a hit 12.5% of time

**Cost** 6