de bello gallico, 4.24

But the barbarians, with the plan of the Romans having been found out, with their cavalry and chariots having been sent ahead, the kind which they were frequently accustomed to use in battles, having followed with their remaining troops, prohibited our men from disembarking from the ships. There was a very great difficulty because of these reasons: because the ships on account of their size could not be anchored except in deep (water), moreover by the soldiers, with the places unknown, with their hands burdened, oppressed by their great and heavy burden of armor, at the same time both it had to be jumped from the ships and position had to be gained in the waves and it had to be fought with the enemy, when those either from dry (land) or having progressed a little into the water, with all their limbs unencumbered, with the places very well-known, threw projectiles boldly and spurred on well-trained horses. Our men, terrified by which things and altogether inexperienced in this type of battle, were not using the same quickness and zeal which they had been accustomed to use in infantry battles.