HOW I WOULD RUN SC2'S NAVAL SYSTEM
Basic combat system is similar to SC1's, except where noted. I won't get into too many nitty-gritty details about how the system works: this is more of an overview. The exact numbers to use are subject to playtest [such as the sub formation discussion below].
Carrier: Consists of 1-2 fleet CVs*, 1 Naval Air Wing [see below], 2-4 CA/CL, and 6-10 DDs. Is highly effective against other surface units, isn't very effective attacking land units or subs, defense vs. air and subs is mediocre [ little worse than Battleships]. Is also FASTER than BB units. Can interdict supply or MPP routes IF Naval Air Wing is present.
Naval Air Wing: Is basically a half-strength (5 hit points) air unit, which can only be based on Carriers [optional: can be based on land]. In other words, the air wing and the Carrier are considered separate entities which can stack, and the Air Wing will sortie to protect the ships when possible.
Battleship: Consists of 1-2 BBs*, 2-4 CA/CL, and 5-9 DDs. Is most effective against other Battleship units, doesn't attack subs very well at all, defends vs. subs decently. Defense against air is decent. Can interdict.
Sub Hunter/Escort Group: Consists of 0-2 CLs and 6-12 DDs, and possibly a CE too when air/ship techs are high enough. Note they would be probably the cheapest naval unit in the game. Is highly effective against subs, defends well against subs, but is vulnerable to other enemy naval units. Fastest naval unit: can fill one of two roles. [Optional: Can interdict shipping]
Subs: Approximately 15 subs, give or take 5. Is most effective against MPP or supply convoys: attacks and defends against surface units a bit less well than it did in SC1, but tends to be harder to find than before [i.e. no more "Sub Dives!" stuff; rather, the sub is never seen in the first place]. Is not effective against other subs. Cheaper than in SC1 by about 50%.
Transports: : Used to transport ground units across the water: can also be used for amphibious operations. Benefits to a limited extent from Shipbuilding and Radar techs. Units on board suffer supply and hit point losses if at sea for too long (more than 3 turns).
Land-Based Air: [mentioned here because it can affect the sea war] Is effective against surface ships [Naval Air is a bit better, being specialized for the role] and other Air Units. Isn't very effective against subs until Radar tech starts taking effect [see below]. Can raid or interdict if a convoy route is within range. [i will leave the Bomber/Fighter/TacAir debate out of this]
Techs affecting naval ops:
Shipbuilding: Represents advances in ship engineering and construction: affects all surface units to one extent or another. However older units [who were built at a lower Shipbuilding tech level] only receive a limited benefit [in that a Nelson class BB can't be made equal to an Iowa class BB, no matter how extensive the overhauls]. "Gun-Laying Radar" is replaced by this tech.
Sub Tech: Affects submarine operations only, making them harder to see and to sink, and increasing attack success against ships and convoys. A high level Sub would basically trump high level Radar, since the periscope/snorkel presents a poor radar signature. [Optional: for balance Shipbuilding tech impinges on Sub tech to a certain extent, thus you basically would need both at high levels to get those Type XXIs working before 1945]
Sonar: Affects ability of surface ships to locate and sink subs.
Radar: Affects ability of both surface ships AND aircraft to locate and sink subs [the latter benefit more]: also aids in ship vs. ship and ship vs. air combat. In part also represents radio-direction-finding equipment.
Jet Tech: Affects effectiveness of all Air Units.
Long-Range Air: With Jet Tech, affects range and effectiveness of Naval Air Units [note: Naval Air has a default +1 edge in range over Land-Based Air]
MPP Convoy System:
MPP Convoys exist to transport MPPs from areas separated from the home country's Capital by water. To create a convoy, go to the Convoy screen, and click on the origin port. Then click on the destination port: a line should appear on the map, skirting intervening land masses [Optional: let players draw their own routes, subject however to lost MPPs over a longer-than-necessary route due to wastage and attrition].
If a Raider is on or within 2 hexes of a convoy line [one hex for a route shorter than 6 hexes], and has been designated as Raiding, MPPs may be subject to loss. This is dependent on the location of the raider [best results if it is on the convoy line-of course it cannot know for sure that it is], the presence of Escorts, the hit points of the raider [lower=fewer MPPs lost], and all relevant techs. All naval units may Raid, except Transports [and optionally H/Es].
Sub Stances: A Sub unit may be designated to be in "Loose" formation: in this attitude the Sub will have more limited success against convoys, and somewhat less success when involved in combat with enemy units on-map. In exchange Subs are harder to find, and suffer less damage if they are involved in combat. This represents a Wolfpack which is spread out [some subs just now leaving port, others returning, etc.], isn't transmitting much, and is not prepared for concentrated operations against convoys. An individual sub however is still a danger, but a Wolfpack's concentrated fire tends to be more efficient...
A Sub unit in Wolfpack mode is a tight closely coordinated group of Subs, being very effective against convoys. However, the success of the enemy researching the Radar tech will greatly cut down on the effectiveness of this Stance, perhaps making Loose the better option [which it may very well be if higher level Subs get made, like the Type XXI, which was designed to work alone]. [basically Radar tech includes RDF tech as well, which was the bane of Wolfpacks from 1943 on]
Aircraft can interdict Convoy routes: simply click on the hex which you want to interdict [in actuality the plane will be considered to be patrolling in a 3 hex diameter around that center point, interdicting the "juiciest" hex in terms of MPPs or supplies-the plane's owner won't know this].
A Hunter/Escort unit may be designated as Escorting a Convoy. To do so, it must be located in the Origin or Destination port. A route has the capacity for 1 or more Escorts: MPPs of the route divided by 10, rounded UP: so a 25 point route may have up to three escorts, and the route doesn't receive optimal protection until that number of Escorts is on duty on that route. Both Escorts and Raiders may take damage: Raiders might take some minor attritional damage on routes with no Escorts. The main purpose of Escorts is to minimize MPP losses on the Convoy route, secondarily to damage the raiders.
[in general, Hunter/Escorts should tend to sink more subs if they are free to Hunt on the convoy routes, but MPP losses will also be higher if H/Es aren't Escorting: quite a strategic dilemma!]
[Optional: A raider has a chance of being spotted if it sinks convoys-or perhaps spotted with a one-hex margin of uncertainty]
[Optional: BB and CV units can also escort, but are only really effective against non-sub raiders: they may be necessary if an enemy surface unit is the one doing the raiding]
Supply Convoys are used to ship supplies to ground/air units operating on a separate land mass from the home country's Capital. They are drawn in the same manner as MPP Convoys: each route requires 10 MPPs per turn (including the first), and will support up to 5 units at a base supply level of 7. To support additional units, the route must be invested with additional MPPs (at a rate of +10), up to a maximum of 30 points. They can be Interdicted and Escorted in exactly the same manner as MPP Convoys, with losses affecting the supply level of the supported troops [either all suffer the same loss, from the HQ on down, or one or more units ends up with 0 supply].
The Atlantic will basically be about double its current size, and also extend more to the North and South.
The US should have a S-N route running from the Carribbean to say New York, simulating the coastal convoys that got ravaged during the 1942 "happy time".
Ships may be stacked in ports.
[Optional: ships may stack at sea in Task Forces: no idea how this might change combat]
Design notes: I want several things to happen here, with the primary emphasis on strategic choice. This system provides a wide range of options for both sides: the Axis can position their subs in a variety of locations depending on the convoys it wants to hit [Murmansk, US coast, Mid-Atlantic or South Atlantic British, etc.], can commit surface raiders if it wishes, can pump up the tech, or just say the heck with it altogether and focus somewhere else. But unlike SC1 the Atlantic should be a viable winning option for the Axis.
For the Allies, it may get even more interesting. They have to decide whether to escort or to hunt, anticipate any German moves [if they assume no commitment by the Germans, and are wrong, it could get VERY costly], and try to close that Mid-Atlantic air gap. It may not be possible to cover all convoy routes, so a triage sort of approach may be needed [at least until the US comes in]-in the real war the British were critically short of escorts in the early going. In the end whoever wins the Tech War should prevail here.