For Italy, Naples is probably the most important, as it can send fleets directly to Ionian or Tyrrhenian, and can also have armies built and put into Apu to defend Venice or Naples.
For Austria- Trieste definitely... without fleets, it is nearly impossible to win, and that is Austria's only sea center so...

I was thinking about Trieste for Austria, but we have to keep in mind that Trieste is almost always occupied. plus how often does Austria demand a fleet unless it is the endgame where home centers just become factories used to produce units on double or triple build turns?

Munich, it's the centerpiece for a lot of stalemate lines, strategically an army in Munich can hold a lot of potential power

at the same time, Austria and Russia are major land powers... they do not have an abundant extra SC on islands near their home. To get what they need, they will have to look towards the Balkans. Normally, in regular diplomacy, Trieste is very important because it's a defensive like against Italy, however, in 7 islands, it seem more likely for Italy to go fight against France over ownership of the Islands there which is why the Italian threat is less... Similar to a regular game, Galacia's ownership could determine who have the upper edge, Russia or Austria... which makes sense for Budapest to be an important center that both keep influenced in the balkans and keep Russia in check...

Here are my thoughts:
England - London. It can get fleets to the areas which are most frequently in conflict, that is, English Channel and North Sea. While Norwegian Sea is important, if you take St. Petersburg it almost ceases to be useful. I find that English negotiations focus on keeping the North Sea and maintaining control of or neutrality in the English Channel. So, London is important. Also, those two are England's best convoy spaces so an army in London is also very useful.

France - Defensively Paris is the most useful because of its adjacency to both Brest and Burgundy. For Eastward attacks Brest falls far behind but it is absolutely necessary for attacking England. Marseilles has a great deal of leverage in the Med, but a fleet in Brest can quickly project similar influence. I think that overall though, I have to say Paris because of its central location.

Germany - I have to disagree with airborne on this one. I would say that Kiel is Germany's most important. It is vastly superior to Berlin for building fleets and an army in Kiel can easily be sent anywhere. While the strategic value of an Army in Munich is very powerful, I think that Germany cannot win without the Sea power that Kiel offers.

Italy - Naples. I totally agree with what butterhead said on this one. Tyrrhenian and Ionian are almost as important to Italy as the Channel and North Sea are to England. Especially the Ionian. Fleets in Naples are very useful for Italy and so is setting up convoys.

Austria - Trieste. As butterhead said, the fleets are important. Also, it provides great leverage to get into Italy which is quite important for Austria's long-term success. While Trieste is often occupied, this increases its value when it is unoccupied because it is much more useful than the other centers long-term. I would also argue that fleets are quite important for Austria to establish a dominant position rather than rely on a powerful naval ally.

Russia - I'm not too sure on this one. I think Russia is the power with the least preference for where to build. St. Petersburg's fleet power is an incredibly useful tool but often Russia gets by for a long time without it. Sevastopol is crucial against Turkey but has little long-term value. Warsaw is the opposite as it is typically useful in the mid-game and end-game but not near the beginning. I think the only one which isn't a contender for most important is Moscow because of its inward position. I think that just because of long-term importance, Warsaw is Russia's most important.

Turkey - Constantinople. As mongoose said it has efficiency for armies and mobility for fleets.

Agree with gman on all counts but France, which I think is possibly the MOST debatable... Brest to hold back England, Paris for its central location, and Marseilles for a southern move...

I actually think Budapest for Austria. It's right in the thick of things. You can afford to temporarily lose Trieste, I've reconquered it many a time and been fine. Losing Bud is often the death knell.

Im with SD on Austria. with Budapest bordering 2 centers and a key region, my vote lies with it.
France is the biggest debate. France cannot get a win with only armies like say Austria can. Brest offers a naval movement to two huge sea areas, plus easy access to Belgium, arguably one of the most important centers in the game.
I like St Petes for Russia. Fleets can be built on either coast to fight either western foe, or an army can be built to cause major damage to England in Scandanavia.

Thanks mongoose998. You've started a very interesting thread and I think you should be glad of the interesting replies you got. I could agree with most of what all the guys said, just noticing that the importance of a HSC (as well as the importance of any other territory) changes when you're expanding rather than when you're defending. Or at the beginning of a game rather than middle rather than ending. But I'd like to look at the question from a different, aritmethical, point of view.

I wondered a question similar to yours, some time ago. Which are the most important territories? So I started building different tables, related to which criteria I deemed the most important each time. The simplest table, assigns a score to each territory, this way:
1) Each bordering territory = +1
2) Each bordering SC (including itself) = +1
So Portugal got 2 Bordering Territories (MAO & Spa) and 2 BSCs (Spa & Por itself): total 4.
This system has some obvious flaws. It doesn't count stalemate lines, first of all. I.E., it looks weird to find StP under average (avg=8.32).
But I believe that this simple table gives to you a good index of the importance of each territory, regarding the possibilities that owning it can give to the owner. This is the table:

North Sea 17
Serbia 12
Kiel 12
Rumania 12
Ionian Sea 12
Mid-Atlantic Ocean 12
Trieste 11
Black Sea 11
Baltic Sea 11
Burgundy 11
Galicia 11
English Channel 11
Budapest 10
Bulgaria 10
Munich 10
Norway 10
Venice 10
Aegean Sea 10
Gascony 10
Tyrolia 10
Tyrrhenian Sea 10
Constantinople 9
Moscow 9
Denmark 9
Smyrna 9
Sweden 9
Ruhr 9
Ukraine 9
Livonia 9
Silesia 9
Ankara 8
Berlin 8
Greece 8
Holland 8
Prussia 8
Rome 8
Sevastopol 8
Spain 8
St. Petersburg 8
Vienna 8
Belgium 8
Liverpool 8
Warsaw 8
Albania 8
Apulia 8
Armenia 8
Picardy 8
Piedmont 8
Gulf of Lyons 8
Norwegian Sea 8
Western Mediterrane 8
Brest 7
Edinburgh 7
Finland 7
Heligoland Bight 7
Skagerrack 7
Adriatic Sea 7
Bohemia 7
Gulf of Bothnia 7
Tuscany 7
Wales 7
Naples 6
Paris 6
Marseilles 6
Irish Sea 6
North Atlantic Ocean 6
Yorkshire 6
London 5
Tunis 5
Clyde 5
Eastern Mediterranean 5
Portugal 4
Barents Sea 4
North Africa 4
Syria 4

So, from this point of view that may look rather abstract (although the question was rather abstract, too), my answers are:

Germany - Kiel
Austria - Trieste
Italy - Venice (Just Because I Can't Say Ionian Sea)
Turkey - Constantinople (Just Because I Can't Say Bulgaria or Black Sea)
Russia - Moscow
England - Liverpool (JBICS North Sea)
France - Brest (JBICS Burgundy)

Interesting list. I'd say the most overrated on it is Baltic Sea (11), and most underrated is Tunis (5), personally. The Baltic is pretty useful, but only really against Germany or whoever has Scandinavia. Tunis is a key point in the fight between France, Italy, and Turkey for control of the Med.

Very true, SD. All territories close to a bottle-neck are underrated. So Tun and Nap close to IonS or Edi and Lon close to NthS. Also, I believe that everyone would say that Tyrolia is more important than Gascony, due to its central position. That's why I've drawn some more complex table, this was just my first idea.

Maybe if we draw the map out to number of SC's in one move being two points and SC's in two moves being one point.

interesting table. according to that the most important SC is Serbia, while Belgium and Greece are stuck at the bottom. I agree that Syria has little use. SIDEBAR! What is the use of Syria? I once brought up clyde, and some great points were made, but what can syria be used for? the Lepanto comes to mind, but besides that?

I agree that Syria isn't always in the thick of battle, however it can really make the difference (especially defensively) in a war between Russia and Turkey.

agreed with Raro- it can be used by Russia to get Smyrna in combination with Ankara or Armenia... it can be used by Turkey to support hold Smyrna, it can be used by Italy/Austria to go after Turkey... it can be used as a empty retreat spot in case somebody has to retreat and re-attack Smyrna/Eastern Med, etc...

+1 butterhead for pointing out retreat spot

@Raro, what can syria do that Armenia or Smyrna cant?
@Butterhead, how can Austria use Syria?

England of course can use Syria!

@mongoose- to answer your questions to Raro(since I feel he will have a similar answer)- nothing, they all serve the same purpose(besides Smyrna being a SC)
and to answer your question to me, Austria is capable of getting fleets or convoying armies to Syria to fight Turkey(or defend if Turkey is an ally)

@mongoose
It's true that if Russia has the Black Sea, then Ankara or Smyrna would be just as effective to guard Armenia. However, having an army in Smyrna provides so many more options. For instance, a fleet in Ankara could be used against the Black Sea rather than being married to Armenia, likewise a fleet in Smyrna can do what it does best and help protect the Aegean. Sometimes it can be the difference between having to 'hunker down' and actually having the capability to counterattack and/or expand. Also, if the Ionian Sea or Aegean Sea is under contention (which is frequent), I usually consider occupying Syria a necessity. Very useful for bounces that can save your tail as Turkey. This of course is when the end of the game and you are facing a dominating Italy, Austria, and/or France.

France: Brest (Paris may be better for defense and Marseilles to attack Italy, but Brest is important all the time and against everyone)
England: London (no contest here)
Italy: Venice (Sure, Naples is much more useful than Rome, but a successful Italy needs a lot of armies and Venice is the most suitable position to build armies. Italy only needs two fleets to fend off most early attacks)
Austria: Budapest (Trieste is necessary to win the game, but it is army power that will allow Austria to survive the early game and have a shot at the win, not fleet power)
Germany: Kiel (Germany may lose Munich, recover and win, but I have never seen Germany win after losing Kiel. It is the most centric territory on the board from which to send both armies and fleets)
Russia: Moscow (Moscow is key as it borders all three other home SCs for Russia.)
Turkey: Constantinople (no contest either)

I agree w/ kaug on all accounts

@moongoose. Yes, according to that the most important SC is Serbia as well as Kiel and Rumania. Nothing strange, I believe, if you consider where they are and what they got around.
I'd say that Greece and Belgium are in the middle, rather than in the bottom, since the average score is 8.32. Just wonder why and/or wonder which ones of the territories scoring more than 8 should be under Greece or Belgium. :)

PS re: mongoose's question about Syria

I guess whay I'm suggesting is that all spaces on the board can at times be very useful or essential, depending on the location and size of the engagement. Since Syria can often be easily fortified by the Med. Sea spaces, it's obv that it is not as important as say.. Naples, Smyrna, or Greece. From a base standpoint, Syria is probably the least likely to be essential in the early stages of the game. It's the same case for Clyde on the other side, which I think is even more rarely useful than Syria because Clyde doesn't offer the defensive bonuses that Syria does, aside from being a retreat spot (thx butterhead). Edi usually suffices to protect the northern seas, and Clyde's movements are restristed because it's open on both sides. Clyde is a good thing for the Russian invader, but if you're England and you 'need' Clyde, then you're probably in trouble. Syria provides a thrifty and effective defense, which is what I am gauging in its value.

I'm with Kaug as well.
regarding Clyde, a French army in there is disastrous, and the northern cylde opening can give a good name for urself early on.
if u had to play a game where u had one less home school, which wud u sacrifice? Think offensively and defensively

One less home SC*

If you had to lose one sc from each country I would choose:

England: Liverpool - easily backdoored by France from the Irish sea
France: Paris - Mars is really useful defending from the east and Brest can build fleets that can easily move to many useful locations.
Italy: Venice - You have to keep Naples. Venice is more useful than Rome for army building, but Venice without Rome is too vulnerable, and losing it gives a gap next to Austria, which gives a bit of breathing space.
Austria: Vienna - Need Trieste to build fleets, Budapest gives access to Rum and Serbia, Vienna only gives exclusive access to Bohemia.
Turkey: Ankara - No reason to build there unless the other centres are full.
Germany: Munich - Hard to decide but Mun is difficult to defend and doesn't give that many options at the beginning.
Russia: Warsaw - Also hard to decide, but losing fleets at either side would be bad and losing Moscow makes the home centres too spaced out. Losing Warsaw means its harder to attack Austria at the beginning but it also means its harder to be attacked and Moscow can move North or South in the first turn easily.

I think as Russia I'd give up Sevastopol. It usually requires far more thought than any of the other home centers in 1901.

I think Russia would be viable losing Sev and just being a Northern power or giving up St Petersburg and being a Southern power. Actually Russia should do pretty well with 3 units compared to everyone else with 2.

That whole Black Sea basin is just a massive downer, I hate having to deal with it.

Russia ->St.Pete
Russia can lose St. Pete and survive quite well. There are also more possibilities to create stalemate lines after losing St. Pete than Sevastopol. Warsaw also is more important. Barring an alliance w/ Austria, Russia probably has little chance at success without control of warsaw and galicia

I think it depends on if you are aiming for survival or winning. Russia can survive without St Petersburg, but probably won't get that far.

I think the idea isn't well defined. Would it mean that the lost sc is neutral or its not a supply centre at all. I was thinking the second one and if so then if both Warsaw and Vienna are gone then Galicia is much less important. It might be interesting to try it out in a variant.

I think that Russia needs that starting fleet in Sevastapol or else Turkey will just walk all over him. Russia doesnt really need that northern center in St Petes, one unit up there will usually deter any English Advances.
Venice for Italy, Italy will not have to worry about Austria as much, and can become a major naval power.
Paris for France, Vienna for Austria, Ankara for Turkey.
I would say Berlin for Germany. Munich is needed for a blitzkreig into France, and Kiel is needed for those fleets. Berlin is kind of a more flexible Vienna. It only has exclusive access to one area, but it can build a fleet to send to the baltic (nothing that Kiel cant do better)

Munich is definitely more useful than Berlin, but its also harder to protect being next to Burgundy and Tyrolia. The Munich army often gets sent back there to defend in the second turn, but Berlin is safe enough to send to Holland.