The genesis of the trireme was the old penteconter
("fifty-oar ship") which, in its prime features, was simply a long,
narrow, open hull, with slightly raised prow and stern cabins, pulling
twenty-five oars to a side. There are a few penteconters still in
existence, though the great naval powers have long since scorned them.
It was a good while before the battle of salamis that the Greek sea
warriors began to feel the need of larger warships. It was impossible to
continue the simple scheme of the penteconter. To get more oars all on
one tier you must make a longer boat, but you could not increase the
beam, for, if you did, the whole craft would get so heavy that it would
not row rapidly; and the penteconter was already so long in relation to
its beam as to be somewhat unsafe. A device was needed to get more oars
into the water without increasing the length over much. The result was
the bireme (two-banker) which was speedily replaced by the still
more efficient trireme (three-banker), the standard battleship of
all the Greek navies.