Oswald Forster had not been present when, in June, 1400, the king arrived at Alnwick.

A few days after the coming of the Earl of March, Hotspur received a letter from Sir Edmund Mortimer, the brother of his wife; asking him to send a body of men-at-arms, under an experienced captain who could aid him to drill newly-raised levies; for that one Owen Glendower had taken up arms against the Lord Grey de Ruthyn, and that turbulent men were flocking to his standard, and it was feared that serious trouble might ensue.

Percy was in a position to send but few men, for with war with the Scotch imminent, he could not weaken himself by sending off a large force.

However, he sent for Alwyn Forster.
"I need twenty picked men, for the service of Sir Edmund Mortimer, Alwyn.

I would send more, were it not for the position of affairs here.
What say you to taking the command of them ?" "I would gladly do so, my lord, if it be that there is a chance of something more lively than drilling hinds, and turning them into men-at-arms, which has been my business for years now, without a chance of striking a blow in earnest." "I think that there will be a certainty of fighting, Alwyn.