Trireme Naval strategy in the Peloponnesian War

A schematic view of what the circular kyklos formation would have looked like from above.
A schematic view of what the circular kyklos formation would have looked like from above.

Squadrons of triremes employed a variety of tactics. The periplous (Gk., “sailing around”) involved outflanking or encircling the enemy so as to attack them in the vulnerable rear; the diekplous (Gk., “Sailing out through”) involved a concentrated charge so as to break a hole in the enemy line, allowing galleys to break through and then wheel to attack the enemy line from behind; and the kyklos (Gk., “circle”) and the mēnoeidēs kyklos (Gk. “half-circle”; literally, “moon-shaped (i.e. crescent-shaped) circle”), were defensive tactics to be employed against these manoeuvres. In all of these manoeuvres, the ability to accelerate faster, row faster, and turn more sharply than one’s enemy was very important.

Athens’ strength in the Peloponnesian War came from its navy, whereas Sparta’s came from its land-based Hoplite army. As the war progressed however the Spartans came to realize that if they were to undermine Pericles’ strategy of outlasting the Peloponnesians by remaining within the walls of Athens indefinitely (a strategy made possible by Athens’ Long Walls and fortified port of Piraeus), they were going to have to do something about Athens superior naval force. Once Sparta gained Persia as an ally, they had the funds necessary to construct the new naval fleets necessary to combat the Athenians. Sparta was able to build fleet after fleet, eventually destroying the Athenian fleet at the Battle of Aegospotami. The Spartan General Brasidas summed up the difference in approach to naval warfare between the Spartans and the Athenians: “Athenians relied on speed and maneuverability on the open seas to ram at will clumsier ships; in contrast, a Peloponnesian armada might win only when it fought near land in calm and confined waters, had the greater number of ships in a local theater, and if its better-trained marines on deck and hoplites on shore could turn a sea battle into a contest of infantry.” In addition, compared to the high-finesse of the Athenian navy (superior oarsmen who could outflank and ram enemy triremes from the side), the Spartans (as well as their allies and other enemies of Athens) would focus mainly on ramming Athenian triremes head on. It would be these tactics, in combination with those outlined by Brasidas, that led to the defeat of the Athenian fleet at the Second Battle of Syracuse during the Sicilian Expedition.

Source: Wikipedia

A schematic view of what the circular kyklos formation would have looked like from above.
A schematic view of what the circular kyklos formation would have looked like from above.