Morale and Fatigue

Fatigue is a hidden statistic within the game. Each ship has their own fatigue value. It ranges from 0 to 100 and has various boosts and penalties associated with it.

A high value of fatigue can be seen as an actual lack of fatigue. A value above 50 is commonly known as the "Sparkle" effect.

Fatigue regenerates at 3 points every 3 minutes (like Fuel, Steel and Ammo) and this regeneration is capped at 49 points, where it will simply stop regenerating.

Specific effects

Above 50, the ship generates a "Sparkle" on its image. This state of fatigue improves performance in general and has a chance to produce the "Great Success" from expeditions. There is no data to suggest that a value higher than 50 (The first threshold on which the Sparkle Effect appears) boosts performance further than 50.

At range 49 to 40, nothing happens.

At range 39 to 30, the "Mamiya Food Ship" button in the fleet composition window is flashing. There is no performance penalty yet.

At range 29 to 20 the ship shows a sad, orange smiley on it's face. This decreases general performance. At this point, regeneration of 3 points every 3 minutes is still functioning.

At range 19 to 0, the ship shows a screaming, red smiley on it's face. This severely decreases performance.

It takes about 20 minutes to go from absolute zero to Orange and another 10 to go from Orange to normal.

There is currently no proof that ships will sink more easily under a low fatigue state. Given the performance cut they get, it is, however, not advisable to take them to battle like that in general.

Fatigue modifiers

1. Returning to base after a sortie always incurs a 15 point loss. It does not matter if you finished the map in any way, were forced to retreat because your flagship was reduced to red health or you withdrew manually, the loss is always 15 points. This loss is subtracted from each ship after points gained during sortie were added. This makes the maximum possible fatigue 85.
2. Returning to base after an expedition causes a 3 point loss which is only relevant if the ship has abiove 50 Fatigue points as the natural regeneration of even the shortest expedition would be 15 points. At maximum fatigue (85, for practical purposes) it is possible to run 12 expeditions before the sparkle effect vanishes.
3. Returning to base after an exercise (PVP Match) incurs no penalty, making a maximum fatigue value of 100 possible.
4. Battle Ranks: A Complete Victory (Regular S Rank. Not Perfect Victory, which is S Rank + No damage taken) boosts Fatigue of the sortied fleet by 1. Defeat (D Rank) decreases the value by 3 for everyone.
5. MVP and Flagship position: MVP grants +10 points to the ship while the Flagship gains +3 points. This stacks, giving a MVP Flagship +13 points. S Rank stacks on this as well, elevating it to +14 points. This applies regardless of battle rank.
6. Night Battle: Starting a night battle incurs a 2 point loss for the entire fleet. Unconfirmed if this is the case with maps that are Night Battles by default but unlikely.
7. Remodel: Remodel resets fatigue to 40 regardless of what it was before
8. Repair: Fatigue is reset to 40 after the repair is finished but only in the case of Fatigue being 39 or less.
9. Time: Fatigue regenerates up to 49 at a rate of 3 points every 3 minutes. It will never decrease over time naturally, meaning that high (>=50) Fatigue, aka sparkling, will never vanish unless the ship goes on a sortie, expedition or loses a PVP match with D Rank.
10. HP: At this point there is no information regarding Fatigue loss based on HP lost. However, some loss seems to occur upon losing percentages of maximum HP.

Gaining Fatigue with maximum efficiency and minimum cost

Running 1-1 solo:

Initially you incur -15 Fatigue. As this map has 2 battles you are guaranteed +26 from Flagship + MVP in both nodes. This gives us the base value of +11. This can be modified by Night Battles (Avoid, even if it would boost you from a B or A to an S rank as you would still lose 1 point) and battle ranks. With both S ranks without Night battle, it would be +13 total (Needing a total of 4 runs for 78 morale and 5 runs for 85 morale)

A D rank decreases the points by 3, a night battle by 2. At the absolute worst outcome (Double D rank, double night battle) you would only gain one Fatigue point in total. (-6 for 2x D rank, -4 for 2x Night Battle)

The best way would be to get through with as little damage as possible and repeat 3 (Assuming decent luck and a constant S rank in the first node and no D rank in the last as well as no night battles = +12 average gain per sortie. 12x3 = 36. 36+49 = 85) times, repair in-between as needed.

Just doing the first node will result in -1 Fatigue, even if you perfect S rank it without a night battle. (-15 + 13 + 1 = -1)