http://www.idbsu.edu/courses/hy101/peloponn/07.htmThe Peloponnesian War - Page 7 of 17
The democrats soon gained the upper hand, led by Cleon. This man, a tanner by trade, argued for an invasion of the Peloponnese and an assault on Sparta itself. The Spartans, he said, would never dare attack Attica with an Athenian army in their homeland, and an invasion would likely spur a revolt of the helots.
So, Cleon got an army and he invaded the peninsula in 425 at Pylos. The invasion was a near thing, but in the end it failed. A few years later, in 422, Cleon died in battle.
This whole period is called the Archidamian war, after one of
the kings of Sparta at the time. In general, despite the effort at Pylos
and
Sphacteria, the first ten years of the war are marked by minor defeats
and minor victories, with neither side able to do the other serious harm.
All the time, of course, trade suffered and there were problems
with allies. And all the time, the oligarchs were urging peace.