Harcla had sent the horses to the rear and his knights and pikemen were deployed on foot to hold the north part of the bridge. One source claims that Harcla broken the wooden bridge. This would have been a logical action, especially if their primary objective was defensive - to stop Lancaster crossing the river while waiting for the main royal army to arrive from the south. Other pikemen and archers were placed at the ford. The main problem in interpreting the deployments is the fact that none of the contemporary accounts specify how close to or on what side of the bridge this other crossing was.

The pikemen were deployed in ‘schiltron, after the Scottish fashion’, that is in the form of a shield. The Cumbrian troops will have been very familiar with this tactic from their action against the Scots, which the latter had proven was a very effective infantry tactic to hold a cavalry attack, and heavily armoured cavalry was the rebel army’s great strength. Soldiers thus deployed in schiltron, like the more famous late medieval Swiss and German pike, seem to have been the precursor of the well disciplined and close order formations of pikemen typical of 16th and 17th century infantry action across Europe.

The use of pikemen in schiltron was an effective defensive answer to cavalry and, according to the Lanercost account, appears to have been the main or first body defending each crossing. However Harcla was also able to deploy the most effective offensive medieval weapon against cavalry, the longbow. Within a few years it would show its devastating effectiveness in halting cavalry in the famous battle against the French at Crecy, but at Boroughbridge, if on a smaller scale, it was used with the same effect.

The rebel forces left the town in two columns to engage Harcla. One, comprising knights and men at arms under the command of the Earl of Hereford, was to advance on foot with a force to take the bridge, which was too narrow for a mounted attack in battle array. The other, under Lancaster himself, was to mount a cavalry attack on the ford. Only one source implies that both sides deployed archers, while none of the descriptions of the action suggests involvement of a significant number of archers on the rebel side.