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 assault 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
Lord Tywin Lannister
Lord of Casterly Rock,
Warden of the West
Command level 6 
War Council level 0
Standard 
Lord Roose Bolton
Lord of Dreadfort
Command level 6
War Council level 0
Victory Conditions
8 Banners
The commander units are worth an additional flag each.
This represents the capture of that individual leader. The markers are simply meant as a reminder of which units contain a commander. Substitute as necessary
Briefing
Winning an expensive alliance with House Frey, King Robb crosses at the Twins with his knights and Roose Bolton marches south to meet Lord Tywin with additional forces from Lord Frey. Even bolstered with additional troops Lord Bolton is outnumbered, especially since King Robb left him only the bare minimum of cavalry. Lord Tywin, believing that he is facing an inexperienced boy for an opponent, arrays a defense with the goal of taking captives, hopefully including King Robb. Lord Bolton, similarly plans his attack around the goal of taking noble captives before his withdraw to the Twins, so as to give Lord Tywin a reason to chase him north.
Special Rules
Ser Gregor Clegane, a massive knight known as "The Mountain That Rides", is famed for his martial prowess. As such his unit is always considered "bold".
The river is completely impassable.