Athens was some distance from its seaport –7 miles IIRC. Not wanting to engage the Spartan army, Athens built the “Long Walls” connecting the two locations, and spent much energy and innovation in schemes to defend these walls –far too long to cover with standing infantry, and thus vulnerable to point attack anywhere, developed a very high efficiency point defense, a cavalry with signal corp combined system, that did secure the Long Walls.

However, out of sight, and secretly (secrecy a weapon Athenian open society could not exploit), Sparta had put together a small navy, which immediately, by pressuring the port itself, devalued the Long Wall sunk cost, which tho necessary, was also far too expensive for something so easily flanked (see Maginot Line).

Had Athens early on determined to meet Spartan strengths head on, win or lose the war would not have lasted three decades, and would not have ended the Golden Age of Greece –which had begun with Alexander’s conquest of Persia.

i think that’s how it played out –don’t quote me –