William, the duke of Normandy: 1048 to 1060

It is a mistake to obviously divide an army in the face of an enemy; it is foolish in the extreme to do so openly in the face of a superior enemy force.

Count Geoffrey of Anjou prevails upon king Henry to ignore you, and to fall upon the portion of your army which you left to guard the approach to Rouen. It is vanquished easily and the city placed under siege. Unfortunately for you, the forces at your command are now utterly inadequate to break the siege, and so you are faced with the loss of your capital city, a serious blow to your prestige. You need a better grasp of strategy. But your chance of getting it is limited by now: You can either parley with your king,or:
Withdraw to Flanders, hopefully to get military aid from your father-in-law, or:
Return to England to get help from king Edward.
If none of these expedients seem promising, then simply attack recklessly as you have done in the past and trust to fortune: toss that coin, be honest, and heads you win tails you lose. If you lost you are dead. If you win, then go HERE.