Historical Notes
In the early days of the War of the Five Kings, King Robert Stark, King of the North, raised an army to march south in support of the House Tully and the riverlords along the trident river, who were under assualt by House Lannister acting as Justicars to the young King Joffery
Baratheon I.
King Robb was faced with a dilemma. The Green Fork of the Trident River lay before him, running from the west of him to the south all the way to King's Landing. Riverrun, the primary castle in the riverlands and the seat of House Tully, laid on the other side of the river and was
under seige from a Lannister Host under the command of Ser Jamie Lannister, knight of the kingsguard, called "Kingslayer", who was preparing to assault the walls. On the other hand, on the eastern side of the river, Lord Tywin Lannister had his own sizable force raiding and looting the countryside on his way slowly north. If left unchecked, Lord Tywin's host would slowly move north until it reached King Robb's own lands, and likewise if left on it's own, Ser Jaime would storm the walls of Riverrun and King Robb's primary ally would be shattered. Also, in the midst of all of this, the only way to cross the river was at "the twins", two castles on either side of the river with a massive stone bridge spanning between them, and seat of the notoriously shifty Lord Walder Frey.
To solve this problem, King Robb hatched a plan by which he would send his footmen south under the command of the cunning and cautious Roose Bolton to meet Lord Tywin in battle in a faint to draw him farther north while he himself led his entire cavalry across the river to lift the siege of Riverrun. Win or lose, Bolton's forces were to withdraw to the Twins and protect the crossing and cut off Lord Tywin's forces should he continue his march north. The idea being Lord Tywin would be drawn north, far away from any crossing but the twins, while King Robb was far away on the other western side of the river smashing Ser Jamie's forces outside the walls of Riverrun.
Pennant
Ser Jamie Lannister
Knight of the Kingsguard
Command level 5 
War Council level 0
Standard 
King Robb Stark
King of the North and the Riverlands
Command level 6
War Council level 0
Victory Conditions
8 Banners
King Robb and Ser Jamie Lannister are worth an additional banner if captured (their unit is killed).
Additionaly, the Inner Keep of Riverrun is worth an aditional flag to the Lannisters should they be able to capture it. The Lannister player is awarded a flag for occupation of the Inner Keep while he has a unit in the hex. If he ever no longer has a unit there, he loses the additional banner it provides until he can capture it again.
Briefing
Winning an expensive alliance with House Frey, Roose Bolton marches south to meet Lord Tywin with additional forces from Lord Frey while King Robb crosses at the Twins with his knights riding hard for Riverrun.
Gaining the strength of House Mallister of Seagard and a few smaller houses sworn to House Tully, King Robb arrives at Riverrun to find Ser Jamie's army in three large camps separated by The Red Fork and The Tumblestone which come togeather to surrounded the castle. Knowing Ser Jamie to be an impatient being whom had gone on several rangings all ready to challenge bandits whom had been raiding his supply lines and defeat the odd defiant holdfast, King Robb plans a raid at nightfall posed as bandits to bring out Ser Jamie and ambush him in the woods near the castle as he gives chase.
The plan worked flawlessly, Ser Jamie led his knights into the forest after the "bandits" without so much as deploying his scouts to check the area. King Robb's Knights were there waiting for him.
Special Rules
The river is completely impassable except at the fords and bridges.
The bridges are in fact drawbridges. The Stark player, at the beginning of his turn, may decide which drawbridges, if any, are lowered (place the bridges on the appropriate spaces).
While a drawbridge is up, the space is still crossable, but is treated as having a ford there (Place a ford marker there in place of the bridge marker). Draw bridges may only be raised/lowered at the *beginning* of a Stark turn. The space in question must not contain a unit. Once raised/lowered, it remains that way until the beginning of the next Stark turn when it may then be changed.