This page contains information about attribute of ships.
Basic attributes is the attributes that you can see on ship info
Those attributes can improve by enhancement.
Those attributes can improve by leveling up.
Rarity doesn't really correspond to difficulty of obtaining the ship in game, it corresponds more to the ship's historical importance.
(E.g. Eugen isn't that rare in the game, however the rarity of her is 5 because of Bismarck)
Every ship has a background that shows the rarity.
See also: Affection
Any ship whose HP is 25% ~ 50% of her maximum HP is called a "moderately damaged ship". For example, ships with 18/72 and 36/73 HP are moderately damaged, while 36/72 is not and can still operate at full strength. Moderately damaged ship's Firepower, Torpedo, Evasion, AA and ASM is reduced to 60% of her full value.
Moderately damaged CV/CVL does not participate in shelling stage, but can still participate in opening aerial combat.
Any ship whose HP is below 25% is called "critically damaged ship". Critically damaged ship's Firepower, Torpedo, Evasion, AA and ASM is reduced to 30%, which becomes generally useless.
Critical damaged ships (except CV/CVL) only participate in day combat (both 1st round and 2nd round for BB, BC and BM), but they will not do anything in torpedo stage and night combat. Critically damaged CV/CVL is even worse which does not participate in any combat.
If a critically damaged ship exists in your fleet, the "Continue" button becomes red as a warning (see "Retreated" section below). If the flagship is critically damaged, you cannot continue your combats but return back.
When a ship's HP reaches zero in a combat, she will retreat, but will not sink. However, any ship, if she is not critically damaged when she enters a combat, will not retreat in any case (including night combat). The ship's HP may reduce to 1, but any further attack is considered MISS. This is called "retreat protection".
There may be a bug that a non-critically-damaged ship may retreat in a battle. Please contact customer service if this bug occurs.
If a critically damaged ship enters a new combat, the retreat protection will not work. Further attack may let her retreat.
WARNING: if a ship retreats, her affection value is reduced by 50% of the maximum value, and other ships whose levels are higher than 10 in your dock will lose 5% of maximum affection as well.
Low Ammunition Penalty
Ammunition affects attributes as well if the remaining ammunition is lower than 50%. 40% ammunition leads to 80% of all attributes. 30% leads to 60%, etc.