Stephen was a skilled soldier and capable general. He knew that his army was equipped for siege, not for open battle. He was especially short on mounted knights, so he knew he could not rely on the favoured tactic of all medieval commanders - the crushing charage of heavily armoured knights. Instead he put his main strength on foot and in the centre. This was where he stationed himself, beside the royal standard and surrounded by the most heavily armoured men of the royal contingent. With him Stephen had Baldwin fitz Gilbert, Bernard de Balliol, Roger de Mowbray, Richard de Courcy, William Peverel of Nottingham, Gilbert de Gant, Ingelram de Say, Ilbert de Lacy and Richard fitz Urse. These were all noblemen of the middle rank who had brought their men to support the king. We know that Bernard de Balliol had brought 100 knights with him plus a rather larger number of mounted sergeants and infantry. Presumably the others had brought similar numbers of men, more or less.The great nobles in Stephen’s army had their own much larger contingents. Stephen was about to learn, if he did not already know, the limits a feudal army. These great nobles were William of Ypres, Earl of Kent and Count of Flanders, Simon of Senlis, Earl of Northumberland, Gilbert Earl of Hertford; William of Aumale, Earl of York, Alan Earl of Richmond and Hugh Bigod, Earl of Norfolk. As earls these five men were of the very highest rank of nobility. They had been trained for war since birth and were able to raise substantial numbers of knights and other men from their vast estates. It seems that these earls had brought brought retinues of mounted knights with them, and that they still had their war horses with them. Given their high rank they would have felt it beneath their dignity to fight on foot, and Stephen was not the kind of man to insult their honour by ordering them to do so.
from "The Battle of Lincoln 1141" by Rupert Matthews.