For those of you who know Diplomacy support and attack orders, you already know where this is going. For those of you who don't please proceed.
1. RAID orders are resolved at the same time as march orders.
As the game sits you can have 1 territory of equal unit strength hold off against 2 against it.
the definition of SUPPORT as intended.
An army lends its firepower or manpower to assist another army in its advance agains an enemy position.
ie: (3 footmen in Lannisport supports 1 knight in harrenhal to attack 2 footmen in riverrun) this results in a 5 on 2 initial combat value (surely a loss for the greyjoys)
However if riverrun places a RAID token there, he can break the support of the superior supporting force in Lannisport and be on level play (2 on 2).
since raid tokens are resolved LIKE march orders, then timing becomes more critical of WHAT and WHEN you raid.
I understand this isn't on par with how Diplomacy actually resolves breaking of support orders so here i will describe how diplomacy deals with it so you have a frame of reference:
In diplomacy, only one army/navy is allowed in each region. in order to take over (win battles) new territories other adjacent territories may SUPPORT the attack to the new region. It is ordered down on paper as such:
Lannisport supports Harrenhal -> Riverrun
Harrenhal -> Riverrun
Riverrun -> Lannisport
This becomes a situation where it is effectively 2 armies attacking Rivverrun and thusly riverrun cannot attack through a supporting Lannisport to break his support.