Support is an important concept to understand, because support breaks stalemates. Support is not a move order; instead, that unit will remain in place and lend its power to either the move or hold order of another unit. That is to say, you can support a defending unit, or support an attacking one. It’s important to differentiate.
A unit has a power of one. Supported by another unit, it has a power of two. Supported by two units, a power of 3, and so on. More support beats less support.
First rule of support: A unit can only support an area it can move to this turn
In order to support a unit in attack or defense, the supporting unit must be able to move to the province/area in question. In effect, this means armies cannot support battles at sea and navies in coastal territories can’t support attacks to landlocked provinces.
The fleet in (adr) can support the coastal province (tri).
The fleet in the coastal province (tri) can support the fleet in (adr) or other coastal provinces. it cannot support landlocked provinces like (bud).
Armies cannot support fleets in the open water
Supporting an attacking unit
The unit that is giving support must be adjacent to the province being attacked. Note that this means that you don’t have to be next to the allied unit that you are helping, only the enemy unit or province that you are cooperating against.
A valid attack support: The army in Greece supports the Bulgarian army’s move into Serbia.
An invalid attack support: The army in Greece borders its ally, but not the target. It cannot support Bulgaria’s attack into Rumania
The support order must also mention the specific move that the allied unit is making. If the orders don’t match the support will fail.
The Turkish fleet supports a hold order for the army in Bulgaria, but that army attacks Serbia. The support would fail, even if the Bulgarian army was itself attacked (see below)
The same situation with Austrian orders. The Austrians make a supported move from Rumania. Because the Turkish naval support failed (see above), the Bulgarian army only attacks Serbia at 1:1 (bounced) and receives a supported attack (1:2) in Bulgaria. It is dislodged and must retreat or disband.
[Note that you cannot support an attack on a province in general– you must specify a unit that you are supporting. If that unit doesn’t attack then nothing happens]
Supporting a defense
The unit that is giving support must be adjacent to the unit it is supporting. This is different from supporting an attack.
The army in Serbia can offer support for a hold order (defensive support) to the fleet in Trier or the army in Rumania.
A common defensive tactic– mutual support orders. Vienna supports Budapest and vice versa. They both defend at two strength.
However! Support can still be cut. Here an attack from Bohemia cut’s Vienna’s support to Budapest. Budapest will be dislodged by the supported Russian unit at 2 to 1. For more information see cutting support
So to recap: Giving support orders varies for attack or defense. A support order given to a moving unit that doesn’t specify where it’s attacking will fail. A defensive support (or a unit remaining in place) will succeed. In this case the army in Serbia only has to say it’s supporting the army in Budapest.
Units can still cause stalemates even when being dislodged
reference: p.9 diagram 12 “The rules in full”
All of these actions are resolved simultaneously. Therefore, although the Germans are forced to retreat from Munich by Austria (1:2), they still cause a stalemate with Russia in Silesia (2:2)
The result. The Austrians take Munich and no one gets Silesia
So can an outnumbered unit always kamikaze attack in one direction to disrupt an attack plan? Not exactly. Ref. p.9 diagram 13 The Rules in Full:
The Austrian Army in Rumania dislodges the Turkish Army in Bulgaria with support from Serbia. The Turkish Army, and the Austrian army in the northeast are both ordered to Rumania, which would normally cause a standoff. However, because Rumania dislodged the Army in Bulgaria, the Turkish attack on Rumania has no effect at all. This allows the Austrian army in the Northeast to enter Rumania during the same turn.
In short, the rule states that a unit can never have an effect on the province that dislodged it.
[Exception and example for provinces from where the dislodge comes from]