After this brief interval, war again broke out. Edward, at the head of his Saxons and Mercians, over-ran and plundered Northumbria. In the following spring, the Danes retaliated, and attacked Mercia on each side of the river Trent. While Edward was busy on the south-eastern coast, repairing and collecting together his ships, a rumour circulated amongst the Danes that he had gone over to the opposite shore with his fleet. Misguided by these tidings, the Danish army passed across the country in the direction of the Severn, plundering every place they approached, and moving about in that irregular manner which showed that they were not apprehensive of any attack. Great was their surprise when they saw a powerful army approaching them; they discovered not the danger until it was too late to fly from it, for Edward was upon them, and there was no alternative but to fight. The battle took place at Wodensfield, and thousands of the Danes were slain, for, beside many earls and chiefs, they left two of their kings dead upon the field. The result of this battle established the power of Edward, and insured the safety of the Saxon kingdom. Like his father Alfred, he trusted not to the chances of war alone for security, but protected his frontiers by a line of strong fortresses, and placed a powerful guard over such weak points as had been most open to the invasion of the enemy. He filled these garrisons with chosen soldiers, who, united with the provincials or militia which Alfred had established, rushed out upon the Danes the moment they approached, without either awaiting the command of the king or of his earls, and by such watchful energy they ever kept the enemy in subjection. Inheriting her father's bravery, Ethelfleda, who was now a widow, acted in concert with her brother Edward, and made her name a terror to the Danes on the frontiers of Mercia, so that the governorship which had been intrusted to her husband Ethelred lost none of its power in her hands.