So you want to play the strongest power with the best possible chance of success, possible win, probable draw and virtually guaranteed survival? Choose Japan! No other power has the capacity for early expansion and yet maintain a very strong defence. With only one potentially threatening fleet in Port Arthur, the next being the British fleet in Hong Kong which is three moves away from your homeland, you have little to fear. Your main concern is to make sure that China and Russia do not ally; so long as that target is achieved you are walking it! OK, perhaps that is a little strong, but your only worry once you have kept China and Russia apart is to try and ascertain where exactly are you going to get 24 centres from. l suspect that many games of CD will see Japan taking part in a drawn game, or at worst being 2nd place to a power not very accessible. You can jump quickly up to 14 or 15 centres but after that things get a little tougher. I think the whole Japanese strategy should be very forward thinking. You have to virtually count the centres you want for victory and base your Diplomacy around that goal. Just pushing in every direction will probably see you halted by the other powers, so how should you approach the others....
Britain: There is no reason why the British should be too afraid of you in the early part of the game, you can try and persuade him to loan his fleet in HK in return for favours elsewhere, such as an alliance against the Dutch. This could bring you great benefits as the Dutch are really the only other power able to match your naval power in the Pacific. Rushing south to take the Philippines first is a major blow to the Dutch and a great boost for your power in the east. If you have friendly relations with China and Russia you could consder this option, leaving some of the builds behind to capture later.
The British can also put pressure on China if necessary, and can be a useful tool against the French if they get belligerent. Due to the distance between your respective core areas you should be able to mainatin a good relationship with the British.
From the middle game onwards the British may block your expansion westwards into the Indian Ocean, so, as I intimated before, think ahead; the British alliance will mean you will have to attack China and Russia from where you will get your quota of centres.
China: As China is one of the two potentially damaging nations to your plans he must be considered an enemy on the whole. Expansion is very difficult with a great mass of yellow pieces facing you to the west. You will be limited to going south gaining the Korean peninsular and Sak if you are lucky with a Chinese alliance, from there you will be looking to get into the Indian Ocean for your winning builds. So long as China does not build any fleets you can keep the alliance going for a long time, but I suspect that one of the two of you will have to attack the other in order to actually win. This is one alliance that would need a lot of trust to maintain.
Dutch: Greatest friend or deadliest foe, the Dutch can make or break the middle game for Japan, as an ally you can, between you, combine forces and sweep westwards sharing the Pacific spoils and then concentrating on building armies to convoy into China and Russia. lt surprises me that I have not seen a game that has included a strong Japanese-Dutch alliance. Perhaps the fear of Japan being hemmed in with so many fleets and the Dutch fearing a Japanese attack for that reason too, means the alliance doesn't tend to see the light of day.
The Dutch are the one power with such naval capability who can attack Japan with any force, but you have got to make sure they don't come that far north. The alliance can develop well for an attck on the East Indies. This doesn't usually take too much persuasion.
The overriding problem is your number of fleets, if there are too many you must do something with them and the Dutch are the easiest target. Forethought required on this relationship.
French: Very much the same as the Dutch, but the French are generally weaker and more inclined to go for the centres that you want within the Chinese border. You will come to blows sooner unless the French have gone against the British. With the weakness of the French navy you can co-operate against the Dutch knowing that you will gain the most out of the alliance. In the event the French are getting strong you may need to reconsider the alliance structure. You are generally after the same centres in the Chinese region so a game long allaince is unlikely. Persuade the French to go for China anyway, the Chinese are a big threat to your expansion, so any disruption to China is worthwhile, even if the French get nothing out of it.
Potential puppet power of immense use.
Russia: The only fleet that can be of any nuisance to you is the Russian fleet in Port Arthur. lf you 'bounce' in YS it can hold up your advance, even threaten your chance of getting to the Philippines before the Dutch; so try and agree not to go to YS. Russia can do little with his fleet other than take Sco, Fus or Mac if he wants to annoy the Chinese. Of course it is probably in your best interests to go to YS anyway as it is such a very useful sea area. So what if you annoy the Russians, they cannot do much against you, particularly if you make sure he cannot build a fleet in Vla.
As an alliance, there is no reason why this cannot work very well, you may need to designate the specific cantres each will have in the Chinese region, but Japan having all the coastal centres and Russia all the inland centres seems fair enough. Russia can get involved with a seperate war against Turkey so once the initial attack on China has been successful you can go your seperate ways.
As an enemy. Russia is fairly easy to deal with if he hasn't got Chinese support - if he has you could be in trouble.
Turkey: Although he is the other side of the board, talking to Turkey can initiate a distant alliance of mutual benefit against Russia. With Russia involved in the west you can make the best of it by gobbling up the centres in the east. Furthermore, if you want to ally with Russia, the exact opposite situation occurs, you can get Russia to attack Turkey, taking his attentions elsewhere. If Turkey attacks the British this may help the Dutch and as a consequnce you would be hard pressed to find an outlet into the Indian Ocean. Relations with Turkey later in the game will depend on each others expansion up to that point; usually any meeting of forces will have seen highly successful campaigns by both powers and you will both be looking for the win. I would expect the final showdown to be somewhere in cenral Russia or the Dutch East Indies, or both!!