Page "Alfred the Great" Paragraph 38

This network of well-garrisoned burhs posed significant obstacles to Viking invaders, especially those laden with booty.

The system threatened Viking routes and communications making it far more dangerous for the Viking raiders.

However, the Vikings lacked both the equipment necessary to undertake a siege against the burh and a developed doctrine of siegecraft, having tailored their methods of fighting to rapid strikes and unimpeded retreats to well defended fortifications.

The only means left to them was to starve the burh into submission, but this allowed the king time to send assistance with his mobile field army or garrisons from neighbouring burhs.

In such cases, the Vikings were extremely vulnerable to pursuit by the king's joint military forces.

Alfred's burh system posed such a formidable challenge against Viking attack that when the Vikings returned in 892 and successfully stormed a half-made, poorly garrisoned fortress up the Lympne estuary in Kent, the Anglo-Saxons were able to limit their penetration to the outer frontiers of Wessex and Mercia.