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.
When they arrived at Mytilene, they encircled it with a single wall, in which forts were built at a number of strong positions.
Mytilene was thus at last completely cut off both by sea and land just as the winter set in.