Source A: Thucydides, History 7.70
In 413 BC the Athenian fleet tries to break out of the Great Harbour of Syracuse.
'The battle was fiercer than any of those before ... Many ships met in a small space - for these were the most ships ever to fight in the smallest area, nearly two hundred on the two sides together - so there were few rammings, since there was no room to back away or to break through the line; collisions were more frequent, as ships crashed into each other while fleeing or attacking another. While a ship was coming in, the men on the decks hurled javelins, arrows and stones at it; and once they met, the marines fought hand to hand, trying to board each other's ships. In many places, because there was so little room, a ship that had rammed one enemy was itself rammed by another ... The great noise of so many ships crashing together caused terror and made it impossible to hear what the rowing masters were shouting.'
To what extent did the place where a sea battle was fought decide its outcome? Use Source A as a starting point and your own knowledge.
Model answer
Source A shows how much the place of battle could matter. In the Great Harbour of Syracuse nearly two hundred ships fought 'in the smallest area', so 'there were few rammings, since there was no room to back away or to break through the line'. The Athenians' great skill - the diekplous and periplous - was useless. Instead ships collided, marines fought hand to hand and the noise drowned out the rowing masters. The battle became a brawl, and the Athenians lost. Thucydides shows that the Syracusans had planned this: they strengthened their prows to ram head-on, knowing the Athenians would have no room in a confined space.
Other battles confirm the point. In 429 BC Phormio refused to fight inside the narrow Gulf of Corinth, telling his men that a narrow space was a disadvantage for a few skilled ships against many; in open water off Patrae his twenty ships won. At Salamis in 480 BC Themistocles lured the much larger Persian fleet into the narrows, where, as Aeschylus describes, its ships were crowded together and smashed one another's oars.
However, the place of battle did not decide outcomes on its own. It mattered because of the forces involved: narrow waters helped the side with more or heavier ships, open water helped the side with more skilful crews. Leadership was what chose the place - Themistocles, Phormio and the Syracusan commanders all deliberately picked the battlefield to suit their strengths. Crew skill, ship design, morale and even the weather, such as the wind Phormio waited for, also played a part.
Overall, the place of battle was often decisive in trireme warfare, but chiefly because it decided whether skill or numbers would count; the real key was the commander who chose a battlefield that suited his fleet.
Explanation
Top answers link the geography to tactics (no room for diekplous or periplous, boarding instead of ramming) and use several battles (Syracuse, Phormio, Salamis). The strongest judgement explains that the place of battle mattered through its interaction with skill, numbers and leadership.