What are the rules for when you are allowed to support a supporting unit?

For example, if France has units in Belgium and Holland, are they both allowed to mutually support each other, increasing their defensive strength to 2 each?

Let's say Germany has an Army in Ruhr and a Fleet in the North Sea. If the fleet attacks either Belgium or Holland with support from Ruhr, does this fail?

Or is France not allowed to have two units mutually support each other. Does one have to hold and the other can support the hold, thereby making France guess where Germany will attack?

The rulebook states:

Support can be offensive ... or defensive (supporting a hold, support or convoy order)

What are the circumstances where supporting a support is a valid rule? When is it invalid? I don't see any examples of this in the rulebook.

2 Answers 2


A unit that is supporting is also holding and is always eligible to receive support in its hold.

The relevant quote from the rulebook is:

A unit not ordered to move can be supported by a support order that mentions only its province. A unit that is ordered to hold, convoy, support, or not ordered at all can receive support in holding its position.

The most relevant thing to notice here is that a unit that is not moving is holding. A support or a convoy is also a hold. If a supporting unit is attacked, the unit does not revert to holding (this is a useful flavor justification but is not technically accurate), but rather the unit was holding the whole time. All that happens is that it is no longer able to support in addition to holding as it is under attack (the support is cut).

As a result of this, two units can support each other, assuming they can each legally support the other (based on adjacency and unit type). Since each unit is supporting, they are each also holding, and thus each is eligible for support in holding its position. If one unit is attacked, it's support for the other unit will be cut, but it will still hold and the other unit will support it's hold.

An opponent needs a minimum of three units to dislodge one of your units and thus disrupt your position. They can do this by either doing a doubly supported attack on a single unit, or by doing a singly supported attack on one unit and an unsupported attack on the other unit to cut it's support.

This is consistent with the basic principle of diplomacy: equal numbers create a standoff, whereas superior numbers (eventually) win. Your two units can defend against an attack of two units but not against an attack of three units.

Note that you can also support the hold of a fleet that is convoying an army. This will help prevent the fleet from being dislodged if it is attacked while convoying.

  • If support and convoy are also holds, then why does the rulebook explicitly list them separately? (as in your quote: "ordered to hold, convoy, support, or ...") You also claim that Toon's answer is incorrect "in many ways", but you specify none, and have no support for that claim. An attacked unit cannot support another, so regardless of what you think about the "attacked supporting unit reverts to hold" phrasing, the result is the same. You need three units to dislodge one of the defending units, or four to dislodge both.
    – ilkkachu
    Commented Sep 13, 2018 at 15:42
  • 1
    @ikkachu Toon claims that two units in mutual support need 4 units to dislodge them when the answer is three. He claims that you cannot support a convoying unit when this is patently false. Even if you want to quibble on whether a supporting unit is holding or reverts to holding, these are both material errors in Toon's answer
    – Zags
    Commented Sep 13, 2018 at 15:45
  • @ilkkachu I have removed the note in case that is what was objectionable
    – Zags
    Commented Sep 13, 2018 at 15:47
  • You need two units to dislodge a single unsupported unit, right? How do you use three to dislodge both of two units?
    – ilkkachu
    Commented Sep 13, 2018 at 15:49
  • 3
    @ilkkachu What's relevant is disrupting the defensive position. It takes 4 units to dislodge two units simultaneously whether or not mutual support is legal. Mutual support is important in that it increases the number of attacking units needed to disrupt any defensive units from two to three.
    – Zags
    Commented Sep 13, 2018 at 16:11
  • Units can support eachother. But you are not supporting the support. You are supporting a hold.

If a supporting unit is attacked, it needs to defend (hold) so the order defaults to hold. And now because of the mutual support, the held unit receives support from the other unit. You can try this using a decent diplomacy tool (for example jDip).

If both units are attacked, they both hold without support. So "the enemy" needs at least 4 units to dislodge both.

  • 1
    You seem to be saying that if the Belgium and Holland units are supporting each other, and the Holland unit is attacked, then the Holland unit switches to Hold, and the Belgium unit supports it. But that doesn't answer the question of what happens if both are attacked. Presumably, both switch to Hold, and neither are supported, but your answer doesn't directly say so. Commented Sep 12, 2018 at 15:47
  • The key insight from your answer is great: "A supporting unit that is attacked reverts to a hold order." Thank you for recommending jDip. That tool really helped me play out a few scenarios to see how the rules work. jDip resolves this scenario exactly as you described. For me, it just feels weird that you are able to double the strength of two units with mutual support. My guts tells me that support of support should not be allowed at all, and that you should only be able to support holds, moves, and convoys. I guess I am wrong.
    – aherriot
    Commented Sep 12, 2018 at 17:31
  • 2
    Basically you either support a unit that is not moving (which includes units that are providing support and fleets that are part of a convoy), or you support a unit in a particular move.
    – ConMan
    Commented Sep 12, 2018 at 23:06
  • It seems like when two units mutual support each other, then both armies are doubling the strength in both territories (total strength of 4 from 2 units across 2 territories). I feel like the player should be forced to choose one territory to get the extra defensive strength.
    – aherriot
    Commented Sep 13, 2018 at 1:18
  • 3
    @aherriot you can dislodge one of the mutually supporting units with an attack from 3 units, which is the minimum "outnumbering force". You don't strictly "double the strength" with mutual support
    – Caleth
    Commented Sep 13, 2018 at 11:39

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