Viking warriors were well known for their close quarter fighting style was based on rapid attacks, go in, attack, get the goods, and then get out before any more backup could arrive. Vikings had a fearsome reputation across Europe.
The Viking “berserker warriors” were the most feared of all.
The berserkers were described as "Odin's men." They were often described as fighting together in bands of twelve or thirteen, and mention is made of the brotherhood of berserkers. It seems that the berserkers worked themselves up into an hysterical frenzy or fury allowing them to access hysterical strength. This strength brings with it increases in reaction speed and coordination which granted them a formidability in battle. This fury, which was called berserkergang, occurred not only in the heat of battle, but also during laborious work. Men who were thus seized by the fury performed things which otherwise seemed impossible for human power.
The word "berserker" today applies to anyone who fights with reckless abandon and disregard. "Going berserk" in this context refers to a state induced by adrenaline in the human body and brain leading a soldier to fight with fearless rage and indifference, a state strikingly similar to that of the 9th century berserkers.