History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
Such were the allies of each side and the preparations they made for the war.
Immediately after the affair at Plataea the Lacedaemonians sent word around to the various states in the Peloponnesus and their confederacy outside the Peloponnesus to make ready such troops and supplies as it was appropriate they should have for a foreign expedition, their intention being to invade Attica.
When everything was ready in the several states, two-thirds of the contingent of each state assembled at the appointed time at the Isthmus.
And when the whole army was assembled, Archidamus, the king of the Lacedaemonians, who was to be the leader of this expedition, called together the generals of all the states as well as the chief officials and the most notable men, and exhorted them as follows:
" Peloponnesians and allies, our fathers made many campaigns both in the Peloponnesus and beyond it, and the elder men also amongst us do not lack experience in warfare, yet never before have we taken the field with a greater armament than this; but though we were never more numerous and puissant, it is also a very powerful state we now go against.