Several new gameplay mechanics are implemented in each new Event, some of which are Event-exclusive. These mechanics may change gameplay drastically, and the event-exclusive ones are described here.

Event-Exclusive MechanicsEdit

Combined FleetEdit

Combined Fleet in Action

See main article: Combined Fleet

The Combined Fleet system was first introduced during the Summer 2014 Event, and has been present since as an event-exclusive mechanic. In a Combined Fleet, you'll have to organize and sortie the first two fleets together, allowing for up to 12 ships (instead of the usual 6) to be sortied out at once. Combined fleets can only be sortied to maps that require it.

Ship LockingEdit

Introduced in the Summer 2014 Event, this mechanic locks ships that were sortied out to specific event maps, and will be unable to participate in other ship-locked maps.

Ship Lock

Example image from 2015 summer event: Different colors represent the fleets that you can use on the certain operations

A ship girl will receive her map lock as soon as she sorties to a ship-locking event map. Afterwards, it's impossible to remove the lock till the end of the event. Remodeling or marriage will NOT remove the shiplock. However, this locking only applies to that ship's specific ID, so any other ship with same name will not have the same lock. Support expeditions will not receive locks.

Here's an example using the Summer 2015 Event:

  • Sending Shimakaze to E-1 and/or E-2 would lock her to E-1 and E-2 and thus unable to participate in the subsequent maps sans the final map.
  • Sending Nagato to E-3 would lock her to E-3 and E-6 and thus unable to be sent to Map E-2, E-4 or E-5.
  • Sending Kongou to E-4 would lock her to E-4 and cannot be sortied out to any other map sans the final map.
  • Sending Yamato to E-6 would lock her to E-6, but she can also participate in E-3 which has the same tag.
  • Sending Kitakami to E-5 would lock her to E-5 only, effectively locking her out from the rest of the other event maps.
  • Sending Akitsu Maru to E-7 won't lock her, and she is free to sortie to any of the earlier event maps until she is actually sortied to any of them, where their respective ship locks would then be applied.
  • All the aforementioned ships are able to sortie to E-7 on Hei-rank (Easy). However, Kitakami would be unable to sortie there at higher difficulties as E-7 does NOT allow locks from E-5.

This mechanic varies for each and every event, so make sure you check the specific Event pages themselves for more info on how the maps are locked. This is also a reason to keep multiple ships per ship-type prepared. If you lack in certain ship-types, you may not be able to fulfill branching routes on later maps, or may be forced to use an sub-optimal composition.

Support expeditions do not check for ship locks, with the exception of the Summer 2014 Event (AL/MI).

Difficulty SelectionEdit

Each map in this event has four (4) difficulty levels (a.k.a. operation ranks) the player can choose from:


The operation rank affects enemy patterns, boss health and strength, the number of times the player has to sink the boss in order to clear the map and the drop rates of ships. Different ranks reward different medals, pieces of equipment and/or materials upon clearing a map. The higher the operation rank, the better the reward.

However, new ship rewards are available on all difficulty levels, and you only have to clear the final event map on Hard to get the exclusive First-class medal.


Click that option circled in as shown in red to change difficulty

You can choose the difficulty level for each individual map separately. However, you will NOT be able to select Hard for a map if you cleared the previous map on Casual/Easy. You must clear the previous map at least on Medium/Normal.

  • NOT POSSIBLECasual/Easy > Hard
  • POSSIBLE(Medium/Normal)/Hard > Hard
  • POSSIBLECasual/Easy/(Medium/Normal)/Hard > (Medium/Normal)
  • POSSIBLECasual/Easy/(Medium/Normal)/Hard > Casual/Easy
Winter Difficulty Settings

Un-highlighted words indicate Current Difficulty

It is also possible to change the difficulty level afterwards, however:

  • If you drop to a lower difficulty (e.g. from Hard to Normal/Easy), the current HP/TP bar value (the one you have the moment you drop down) will increase by 25% of the new maximum and you will retain ALL unlocking/phases done on the previous difficulty level.
  • However, if you change to a higher difficulty (e.g. from Easy to Hard), the boss's HP/TP bar will be reset upon doing so and ALL unlocking/debuffs/phases will be reset as well. In short, you will lose your entire map progress!

Once the map is cleared (boss HP bar is depleted, boss is defeated, and the HP bar is no longer visible in the map):

  • You CAN NO LONGER re-adjust the difficulty level, but can still farm the map on the difficulty you have chosen to clear the map with.
  • The enemy patterns revert back to pre-final patterns.

Map-specific Mechanics Edit

  • Transport escort fleet visits a "flag node". Here the player has used only Drum Canisters
  • Transport mission success
  • Transport mission failed

First introduced in the Fall 2015 Event, this map mechanic requires that players deplete a gauge known as Transport Load-Off gauge by reaching a drop-off point, then attaining at least an A-rank victory at the boss to secure said point. Ships are able to equip Drum Canister, Daihatsu Landing Craft, and other related equipment to increase the amount of gauge depleted with each victory. Depending on the map, players may be allowed to set up a type of Combined Fleet known as Transport Escort Fleet (輸送護衛部隊 yusou goei butai) to perform this role.

The player's fleet is required to visit a node indicated with a flag. From there, the game will note how many Drum Canister & Landing Crafts the player's fleet has carried to that node. The player's fleet is then required to get an A rank or higher at the boss node in order to deplete points off the Transport Load-Off gauge. (揚陸成功した輸送物資量? youriku seikou-shita yusou busshiryou)

In the case of the Fall 2015 Event, E-2 utilized the Transport Load-Off gauge, but was designed for a single fleet. Fall 2015 Event's E-3 used a Combined Fleet, with the Transport Escort Fleet (輸送護衛部隊 yusou goei butai) option enabled. Fall 2015 Event's E-5 had a dual gauge system, where after depleting the TP gauge, the HP gauge would be revealed and would have to be depleted again to truly clear the map.

Difficulty selection applies to this mechanic the same way it does to HP gauges.

Fall 2016 Event
Ship/Equip Type S Rank
TP added per ship in fleet
DD? 5
CL? 2
CT? 6
CAV? 4
BBV? 7
AV? 9
LHA? 12
AO? 15
AS? 7
TP added per equipment in fleet
Drum Canister 5
Daihatsu Landing Craft 8
Daihatsu w/ T89 8
Ka-Mi 2
Combat Ration 1
Canned Mackerel 1
Different value applies for each event

Some of the currently known information about the Transport Load-Off gauge mechanism: TP Calculation, according to data obtained from nga178 forum (Chinese), wikiwiki calculation, and a TP Calculator based on the NGA's method (Chinese)

  • TP calculation is not affected on a per-Map basis.
  • According to a source from the Japanese wikiwiki, TP point calculation has been changed since the Fall 2015 Event.
  • In a S Rank victory, after TP calculation, the total is rounded down.
  • In an A Rank victory, after TP calculation, the total is rounded down, multiplied by 0.7, and then rounded down again.
  • The TP Gauge won't change if the boss battle results in a B-Rank or lower.
  • Each Combat Ration grants approximately 1 extra TP. No data for Canned Mackerel or Underway Replenishment yet.
  • How Combat Ration consumption affects the TP value is still unknown.
  • Ships that reach the flag node in taiha (大破) status, or were retreated (撤退 via Fleet Command Facility) are not counted in the node, and neither are their equipment.
  • Other unlisted ship types, like CLT?/CA? have not been tested.
  • Daihatsu Landing Craft related calculations are not accurate and require further data.
  • Improving Daihatsu won't give extra TP[1]

Also known as Boss Debilitation Mechanism

First introduced in the Summer 2015 Event, this mechanism allows the player's fleet to increase the damage dealt to the boss by fulfilling specific requirements on the event map. The exact mechanism varies depending on the map, but it has been present for Extra Operation maps from Summer 2015 onwards with the exception of the Winter 2016 Event & the Fall 2017 Event.

In Summer 2015 Event, this mechanic was only applicable for the Air Defense Princess at E-7. Initial testing indicated that the debilitation nodes were X and Y. However, a source that appeared after the event indicated that node C was also another debilitation node. It was also revealed that the debilitation from node C was triggered by the destruction of Wa-class transport enemies. It is not clear if any Wa-classes or only those from E-7-C were valid. In this event, this mechanic increased all ships' critical damage multipliers and possibly critical hit rates at the boss node.

This mechanic reset at 0000 JST daily.

Other than boss node (node Z) the debilitation nodes are shown.
Summer 2015 E7 Map

Old Red node

Old Red node

Old Red node

The Fall 2015 Event version of the mechanic is applicable for the Submarine Princess at E-4 and the Destroyer Water Demon at E-5, allowing the player to weaken the bosses by fulfilling certain conditions. Unlike the other events which lacked any visible indicators, enemy bosses now have separate CGs and lines to indicate their weakened version.

This mechanic reset at 0500 JST daily.

  • The Fall 2015 Event E-4 boss, Submarine Princess, could be debilitated by defeating the Anchorage Water Demon at Node M and Harbour Princess at node J at least once. While the debilitation is in effect, the gleaming eye will glow with cyan instead of purple, and a green goo would appear to leak out from her body.
Other than boss node (node O) the debilitation nodes are shown.
Fall 2015 E4 Map

Old Red node

Old Red node

During Spring 2016 Event, the Central Princess at Map E-6 can be weakened by scoring an S-rank in the following nodes at least once. The debilitation will take effect when at least two of the nodes are successfully cleared with S-rank, and will be in full effect upon successful clearing of all the designated debilitation nodes, which will be indicated when the word "Masaka" is appended to her introduction line.

Unlike the previous events, this mechanic does not reset throughout the event.

Other than boss node (node N) the debilitation nodes are shown.
Spring 2016 Event E-6 Map

Old Red node

Old Red node

Old Red node

It has been speculated that E5 also contains a debilitation node for the Central Princess at E-6 until Node I has been confirmed on 10th May 2016 Twitter as the debilitation node.

Other than boss node (node M) the debilitation nodes are shown.
Spring 2016 E5 Map

Old Red node

  • Fall 2017 Event E-4 before unlocking Z nodes
  • Fall 2017 Event E-4 after unlocking Z nodes (but before unlocking ZZ nodes)
  • Fall 2017 Event E-4 with Z and ZZ nodes unlocked

The name may change depending on which part of the map is unlocked by the mechanic (i.e. it can be Unlockable Starting point or Unlockable Nodes)
Also known as Hidden Routes.

Starting from Fall 2016 Event, certain maps may have starting point, nodes or pathways that may be hidden at the beginning, which will be opened after certain conditions are met. The conditions for unlocking the nodes varies from depending on the map, but in most these conditions involves reaching certain part of the map and earn an A or S-rank at the specific nodes.

Starting from Spring 2017 Event, map nodes and the path to them can be unlocked at certain maps. The additional routes are always necessary to fully clear the map.

Striking Force FleetEdit

2017-11-19 01-59-52 33
2017-11-19 01-59-54 19

See main article: Striking Force

First introduced in Fall 2017 Event, a striking force under certain conditions, allows the admiral to use the 3rd Fleet,to sortie a 7-Ships Fleet. When it is available, it will be indicated as 第三部隊 on top of the "3rd fleet" icon. See the dedicated page for more info.

Vanguard Formation (警戒陣)Edit

  • Vanguard Formation
  • Striking Force Vanguard Formation
Introduced in Fall 2017 Event for the first time along with the Strike Force mechanic, the vanguard is a defensive formation which affects the ships based on how they are positioned in the fleet.
  • Your fleet is divided evenly between a top half and the bottom half. For example, a fleet of 6 ships will be divided 3/3, with the first 3 ships belonging to the top half and the last 3 ships belonging to the bottom half.
  • However, in case your fleet consists of an uneven number of ships, the top half will take the lower number. For example, if you're using a Strike Force which consists of 7 ships, your top half will consist of the first 3 ships, while the bottom half will be the last 4 ships. The term "top half" and "bottom half" will be used.

Fleet Halves Damage Modifier Evasion Bonus? Aggro?
Accuracy Modifier
Shelling Torpedo ASW Night Aerial
Top half 50% 100% 100% 50% 100%
80% ??? ??? ??? ???
Bottom half 100% 100% 60% 100% 100%
120% ??? ??? ??? ???

Keep in mind that Vanguard has a Night Battle modifier that is not a 100%, which is unique among the available formations. For nodes where you want to maximize your firepower as much as you can, especially on boss nodes, Vanguard is generally undesired.

The ASW capable ships benefit the most from the top half while those who damage through shelling and night attacks benefit the most when placed in the bottom half. Torpedo modifier remains 100% regardless of where the ship is placed in the fleet.

Note that in the scenario that a Shelling Support is used, the Shelling Support will receive a 50% firepower modifier as well when Vanguard is selected. This is applied on the whole support fleet, so placing weaker ships at the top will not solve this problem.

When the Vanguard formation is selected, all your ships in the fleet will obtain a post-cap evasion bonus [1]. While everyone in the fleet will gain an evasion bonus, the amount of evasion you gain is based on 2 things:

  1. Is the ship a DD?
  2. Is the ship part of the top or the bottom half?

The rough estimates of the evasion bonus are as followed:

  • Top half (including the 4th ship)
    • Non-DD: +5% Evasion
    • DD: +20% Evasion
  • Bottom half (excluding the 4th ship)
    • Non-DD: +20% Evasion
    • DD: +40% Evasion

Regarding aggro effect, the bottom half is attacked more often than usual, which is supported by its higher evasion.

A test has been done albeit roughly regarding Vanguard Formation's effect on Air Raid nodes. A conclusion was reached as followed [2]:

Ship Slots Evasion Bonus? Aggro?
First half
Second half

While the aggro effect is still there, you do not gain any evasion bonus against airstrikes. In other words, your evasion will be the same as in Diamond formation, except with a worse AA modifier of 110% instead of 160%.

  • Your bottom half will suffer the most from airstrikes and you do not have evasion bonuses to compensate for it this time.

Other Common MechanicsEdit

LoS CheckEdit

See main article: Line of Sight

Starting from the Spring 2014 Event, LoS (Icon LOS)-based checks have been implemented throughout various maps, which require players to exceed a given LoS threshold in order to proceed to a given node.

Support ExpeditionEdit

See main article: Support Expedition

Land Base Aerial Support (LBAS)Edit

See main article: Land Base Aerial Support

Node-specific DetailsEdit

Aerial node
An aerial battle node

These nodes consist of two Aerial Combat phases, and do not have any other regular combat phases (shelling/torpedo/asw). Each aerial combat phase takes place independent of one another; aside from that, there are no special mechanics.

Raid node
An air raid node

Also known as: Air Raid Battle (空襲戦)

First introduced in Winter 2016 Event.

Unlike Aerial Battle nodes, Air Raid Battle nodes are strictly defensive air battles against an onslaught of Abyssal aircraft, where you try to shoot down as many bombers as possible before they attempt to damage your ships.

There are a few key differences with an Air Raid Battle versus regular battles:

  • Abyssal aircraft will attempt to bomb your fleet (Note that there will be no "plane launching" animation for the abyssal side). Your fleet will launch any aircraft capable of participating in the Aerial Combat phase to intercept them. As such, the only means of directly damaging the enemy at these nodes is through the use of bombers sent to the node via Land Base Aerial Support.
  • Given that it is an air-defense node, it is advised to use diamond (for single fleet/striking force) or ring (for combined fleet) formation in these nodes.
  • These nodes calculate ranks solely based on the damage you take during the air raid:
    • Perfect S: Take zero damage from the air raid. Annihilation of enemy bombers is optional.
    • A: Take less than 10% damage[2]
    • B: Take 10%-20% damage[2]
    • C: Take 20%-50% damage[2]
  • As of the Fall 2017 Event, these nodes consume 6% fuel and 4% ammo. This behavior was extended to regular world maps with the Phase 2 [Block-1] Update.
  • Generally enemies are in the diamond formation, but the formation graphic may look different or not appear due to diamond normally being unselectable with fewer than 5 ships.
  • You cannot choose to pursue the enemy for night battle, as you are not fighting with an enemy fleet, but instead defending yourself from an enemy air raid.

As of the Fall 2017 Event, nodes containing only submarines consume 8% fuel (rounded down, but 1 unit at minimum). This behavior was extended to regular world maps with the Phase 2 [Block-1] Update.

Night node
A night battle node

Night to Day node
A night-to-day battle node

As of the Fall 2017 Event, these now consume 10% fuel and 10% ammo (rounded down, but at least 1 unit at minimum). This behavior was extended to regular world maps with the Phase 2 [Block-1] Update. There is one exception to this rule - yasen nodes containing only PT ImpsPT Imp Pack Banner consume only 4% fuel and 8% ammo.

Events may feature nodes marked as night-to-day battle nodes, which involve a night battle where your fleet fights an enemy combined fleet, followed by a day battle against the enemy main fleet. Proceeding from night to day only occurs when certain requirements are met. When they are met, the transition happens automatically - unlike going from day to night battle, you do not have any control over whether this happens.

  • Winter 2016 Event - map E-2. Game prompts you to select a node.
  • Winter 2016 Event - map E-2. Available nodes are displayed.

Also known as Manual Node Selection

Introduced in Spring 2015 Event, certain nodes allow you click on a node to specify which route you want to take. You may only choose nodes that are connected directly to the node you are currently at.

Starting from Winter 2016 Event, maps with multiple starting points were introduced. These maps may have multiple starting or/and ending nodes. The starting node depends on the ships, or combined fleet type that was used to sortie on the map.

Multiple branching

As shown in the image, there were multiple start and end nodes in 2016 Winter event E-3. The first part was to deplete TP gauge, using a Transport Escort Fleet which started at node A and ends at node S. After which, players had the option of using either a Surface Task Force (Starts at node J) or Carrier Task Force (Starts at node E or F) to make their way to the final boss (node T).


  2. 2.0 2.1 2.2