The Importance of the North of England 1644
York was besieged in April 1644. If York fell and the army of Newcastle defeated, then Charles would lose the whole of the North of England.

This area was a valuable recruiting ground and a large financial contributor to the King's war effort.

It would also mean there would be a block between him and Scotland where he had great hopes that the Marquis of Montrose would bring the Scots to heel.

The King had to keep hold of York until he could bring fresh troops over from Ireland to help.

Prince Rupert was in Shrewsbury recruiting and raising money and supplies. Charles thought he was the obvious man for the job of relieving York.