Are "Diagonal" Attacks More Deadly in Diplomacy?

Question

As France, for instance, it's fairly easy to defend against an extended "frontal" attack in the north by England and Germany, by covering the connected zones, Burgundy, Picardy, and Brest. Fortunately I've never had to do this, but it seems harder to defend against a simultaneous attack by England, aimed at Brest, and Italy, aimed at Marseilles, on a northwest to southeast axis.

As Russia, it's relatively easy to defend against a two power attack from the west or southwest, say by Austria-Hungary, allied with either Germany or Turkey. That's because Sevastopol, the Ukraine, and Warsaw form a natural defense line. The one to fear seems to be England and Turkey to both the north and south. Then Russia is split in two directions, and easy game if one of the Germanic countries becomes a third attacker.

Has anyone had the experience of being victimized by "divergent" attacks at both ends of the Empire? Or more to the point, gone out of their way to create these kinds of problems for their opponents?

Answer 1

It's definitely the case that fighting a two-front war is more than twice as hard as fighting on one front. Besides the obvious reason, that you need twice as many units, there's the support-cut effect too. Most empires, especially early, aren't 3 provinces wide, so even an unsupported attack on one side can strip a unit on the other side of the support it needed to hold.

One place this is borne out is in the aggregate results of Russia. Russia has the highest solo rate of any power, and the second highest elimination rate. If Russia can't turn their initial two-front (North and South) exposure into a one-front war, they're done for in a blink.

Answer 2

There are four main factors that make an attack dangerous in diplomacy:

1. The relative number of units attacking vs defending
2. Adjacency of the territories you are defending
3. How many territories there are surrounding your territories
4. How many sea-land transitions the attacker has to make

In general, more units will always beat fewer units given enough time. A 2-on-1 in the early-game of diplomacy (when everyone is roughly equally sized) results in the death of the 1 unless the political situation shifts. A slower death is only less "dangerous" in that it gives more time for a political shift and thus increases your chances of gaining allies or of the alliance against you falling apart.

The defensibly of Warsaw + Ukraine + Sevastopol is as much about the adjacency of these territories as it is about the fact that Austria and Turkey only have 4 territories to attack from (Galicia, Rumania, Black Sea, and Syria). This limit in attack surface limits the number of units they can actively use to support moves, and thus means you can hold indefinitely with 4 units on the defense. It's actually even more defensible if you lose Sevastapol, as then they have only a 3-territory attack surface (Galicia, Rumania, and Sevastapol). Of course, if Germany allows them into Silesia, this situation changes.

To see why attack surface matters, try defending Galicia + Ukraine + Sevastapol from an attack by Austria and Turkey. This position is vastly harder to hold as it has a 6-territory attack surface even without Germany's territories (Bohemia, Vienna, Budapest, Rumania, Black Sea, and Syria). Galicia will fall almost immediately to a committed attack.

France, similarly, can defend against Italy and Germany more easily than Germany and England because Switzerland reduces the attack surface on France's Eastern side, where their Northern side has no such protection. While England does have to overcome a sea-land transitions to attack Paris (making the attack harder), they still threaten 3 of France's 5 supply centers (counting Spain and Portugal) by sea, which is sufficient to cripple France.

In conclusion, being attacked from countries on different sides is dangerous as a result of the increased attack surface as much as for the inability of your defensive fronts to support each other.