1. A close approach in line-ahead formation towards an enemy would give the attacking fleet an absolutely minimum chance to use its rams but a maximum exposure of its flanks if the enemy closed in his ships from both sides. In contrast, an approach in line-ahead round an enemy flank would be less dangerous, especially if conducted by line-ahead squadrons abreast of each other, since here the inner squadron would protect the outer squadrons and the time of passing the enemy flank would be much reduced. Such a flanking movement would be needed to replace the normal method of attack if the enemy had closed up his line very tightly or blocked the gaps in it by a second line suitably arranged against the diekplous or periplous. A flanking movement by a whole fleet would also be called a periplous, but it was on a large, or strategic, scale not a small or tactical one. At Syracuse the narrowness of the harbour prevented its use by the Athenians, whilst the arrangement of Syracusan ships prevented penetration of their line. Even when such a large-scale periplous was possible the issue still remained to settle, since the defending ships, or at least those on the farther flank, would have had time to reposition themselves and not succumb easily to attack from the rear, although any need for manoeuvre in face of the enemy was likely to cause confusion among weaker crews, so they could hardly have hoped to form a strong line again.
But in the end each encounter had to be decided by any one of at least four possibilities— diekplous, periplous, a direct head-on ram, or an indecisive collision with a subsequent struggle between grappling ships.
