After many months, I figure it is time I finished my rudimentary analysis of the game Diplomacy. For reference, here are links to Part I (game description) and Part II (opening and mid-game analysis).
To briefly recap, the second stage of the game occurs when all (or at least most) of the neutral supply centres have been occupied by one of the seven major powers. Most players are on nearly equal footing in terms of military size, and the number of players means cooperation with at least one or two others is necessary to overcome an opponent (even though the game is zero-sum in terms of any progress made by one player is at the expense of another). The third and final stage of the game is difficult to concretely separate from the second, but it basically happens when some players begin to lose badly and others expand their military to impressive sizes of ten or more units. At this point one or two players may even be eliminated from the game. While in my experience this seems to happen most often to either Germany or Austria-Hungary (being in the centre is an unfortunate place to be), it doesn't always. Russia makes a large and tempting target, and a Russian leader lacking vigilance might find himself victim of a disastrous invasion from the north through Scandinavia, Finland, and the Barents Sea, or from the south (especially if the Turks manage to get a fleet in the Black Sea). Even Great Britain, which is notoriously difficult to invade (but, at the same time, notoriously difficult to expand from) can be defeated, especially if France and Germany team up and devote some resources to developing their fleets. If enemy ships manage to enter the English Channel and the North Sea, the British are in a lot of trouble.
Regardless of who has found their fortunes dwindling and their dreams of European dominance shattered, as the dust settles the remaining juggernauts begin to face the same predicament that spurred the first round of wars: to expand their empires, they need a target to conquer. The difference at this point, however, is that interactions between players are now often more complicated. Many turns have gone by in an alliance against a foe, but with that foe gone, players begin to wonder how long the alliance will continue. Additionally, those doing exceptionally well at this point begin to grow cocky; victory is looking more assured, as their militaries are now three to four times as powerful as they originally began. It is hard to give much analysis for this part of the game, since the situation is virtually impossible to predict. This is also the part of the game that I have the hardest time with, simply because I don't like the concept of backstabbing an ally. While it very often is advantageous to strike without warning (especially if you and your ally are doing equivalently well or he is even doing better), I have a hard time emotionally with that. It might sound like I am making myself out to be a nice guy here, but I'm not entirely sure that is the case, either. It could be a remnant of chivalry that makes me feel this way, but it could also be a testosterone driven alpha-male style arrogance in which I want my foe to know that I'm coming for him and still have no way of stopping me. I like to think it's the chivalry side of things, but who knows.
Anyway, I am wandering away from the topic at hand. Often people actually don't make it this far in Diplomacy (it is an awfully long game for a single sitting), and simply stop after a player or two is eliminated (or even before if time players need to leave) and simply count up the number of supply centres under each person's control, determining rank in that manner. I hope in my ruminations on the subject I have done Diplomacy justice, and perhaps I may also manage to convince some of my readers who actually know me and have always begged off playing to give it a shot.