(Clapham 1910 ; Davis 1989 ; Williams forthcoming: ch. 6 ). Horses provided a similar
mobility on land to that provided by the ships along the rivers and the coast, and
allowed the Vikings to extend the idea of the surprise attack in areas without access by
water.
This emphasis on mobility was coupled with a shrewd sense of where to raid.
Familiarity with western Europe prior to the outbreak of Viking raids enabled them to
target wealthy and isolated monasteries for the early raids, as well as major coastal
trading centres such as Dorestad in Frisia, which was raided repeatedly (Coupland
1988 ). However, the choice of targets became even more important with the shift
towards larger-scale raiding, especially once the Vikings began to overwinter, rather
than simply raiding seasonally. This overwintering is again one of the most distinctive
aspects of Viking warfare, with a significance that has largely been underrated. The
early Viking raids tended to be seasonal, of necessity, since their ships were not well
suited to winter sailing. However, it is easy to ignore the fact that land-based warfare
was normally seasonal in this period as well. Even Charlemagne, despite his impressive
record for conquest and tribute-taking, rarely campaigned over winter, although he
tended to campaign in most years (Reuter 1985 ). Although Alfred the Great eventually
recognised the importance of maintaining a standing army to counter the Viking threat,
this was not easy to maintain, and on one occasion a besieged Viking force was able to
escape because the besiegers were forced to withdraw before their relief arrived (ASC A,
sub 894 [ 893 ]). When even major kingdoms struggled to maintain permanent field
armies, the fact that the Vikings managed to campaign for years on end, often in hostile
territory, is perhaps a more impressive achievement than any success they may have
enjoyed on the battlefield.
They managed to do this by careful selection of overwintering places, descending on
monasteries, towns and royal estates early in the winter. That meant that they arrived in
places where supplies had already been gathered, which they could take over for their
own use, while the onset of winter made it difficult for anyone to raise and supply an
army to remove them before the spring. The Vikings then probably spread out over
the surrounding area, making it easier to supply the smaller groups, but retaining the
centre as a rallying point and defence in case they were attacked, and there is growing
evidence for secondary Viking activity close to Viking overwintering centres such as
Repton, London and York (Brooks and Graham-Campbell 2000 : 69 – 92 ; Richards
2001 : 97 – 104 ; Blackburn 2002 : 89 – 101 ; Williams forthcoming: ch. 6 ). Some sites
already had defences, such as Roman forts and fortified towns, but where they did not,
the Vikings simply created their own fortifications, as at Repton, and the many fortified
centres in Ireland known as longphorts (Price 1991 ; Kelly and Maas 1995 ; Docherty
1998 ; Kelly and O’Donovan 1998 ; Ó Floinn 1998 ; Biddle and Kjølbye-Biddle 2001 ;
Gibbons 2004 , 2005 ; McKeown 2005 ; O’Brien et al. 2006 ; Williams forthcoming:
ch. 4 , 6 ).
While tribute payments provided short-term relief, battles were rarely decisive
enough to provide a lasting solution to Viking raiding (Coupland 1999 : 68 – 9 ), and it
was only when the twin issues of mobility and supply were tackled that the Viking raids
could successfully be contained. Charles the Bald introduced fortified bridges to deny
the Vikings access to the Frankish river system, making it difficult for them to penetrate
far inland, although this strategy failed when bridges were not built or maintained
properly. Fortified bridges were also used by Alfred the Great, who also built ships to
–– Gareth Williams––