Solidus of Emperor Maurice 582-602.

The light-haired races place great value on freedom. They are bold and undaunted in battle. Daring and impetuous as they are, they consider any timidity and even a short retreat as a disgrace. They calmly despise death as they fight violently in hand-to-hand combat either on horseback or on foot. If they are hard pressed in cavalry actions, they dismount at a single prearranged sign and line up on foot. Although only a few against many horsemen, they do not shrink from the fight.
They are armed with shields, lances, and short swords slung from their shoulders. They prefer fighting on foot and rapid charges. Whether on foot or on horseback, they draw up for battle, not in any fixed measure and formation, or in regiments or divisions, but according to tribes, their kinship with one another, and common interest.

Often, as a result, when things are not going well and their friends have been killed, they will risk their lives fighting to avenge them. In combat they make the front of their battle line even and dense. Either on horseback on foot they are impetuous and undisciplined in charging, as if they were the only people in the world who are not cowards.

They are disobedient to their leaders. They are not interested in anything that is at all complicated and pay little attention to external security and their own advantage. They despise good order, especially on horseback. They are easily corrupted by money, greedy as they are. They are hurt by suffering and fatigue. Although they possess bold and daring spirits, their bodies are pampered and soft, and they are not able to bear pain calmly.

In addition, they are hurt by heat, cold, rain, lack of provisions, especially of wine, and postponement of battle. When it comes to a cavalry battle, they are hindered by uneven and wooded terrain. They are easily ambushed along the flanks and to the rear of their battle line, for they do not concern themselves at all with scouts and the other security measures. Their ranks are easily broken by a simulated flight and a sudden turning back against them. Attacks at night by archers often inflict damage, since they are very disorganized in setting up camp. Above all, therefore, in warring against them one must avoid engaging in pitched battles, especially in the early stages. Instead, make use of well-planned ambushes, sneak attacks, and stratagems.”

Excerpt From
Maurice’s Strategikon. Handbook of Byzantine Military Strategy by Emperor Maurice (582 – 602 AD)
Dennis, George T. (trans.)