The Pale Horseman by Bernard Cornwell

The Pale Horseman (The Saxon Chronicles Series #2) - Uhtred having sworn fealty to King Alfred is now fighting with the Saxons. He has fought at the battle of Cynuit, but Odda the Younger has taken credit for his feats. Alfred has negotiated a peace with the Danes. While he is waiting for future developments, Uhtred decides to patrol the coast of Wessex and Cornwalum. He meets Svein, a Danish warlord and they fight together in the seas south of Wales. When Uhtred returns he is summoned to Alfred, while the council is deciding Uhtred’s punishment for trumped up charges, the Danes attack and King Alfred is forced to take refuge in the marshlands of Æthelingæg. With Uhtred’s help, Alfred gathers together an army to attack the Danes.