In the course of my Master’s studies, I discovered a number of curious and unsettling details which are well known to specialists but not by the interested public. One of these is that we know very little about what happened for a year of the Peloponnesian War, and that we are not sure where to fit this year into the accounts which passed down to us. As this may sound surprising, I will explain.
When Thucydides died, his history of the Peloponnesian War was unfinished. He left a clear statement of the length of the war and a chronological system based on summers and winters which was meant to avoid the vagaries of the many calendars used in Greece. Thucydides’ account begins in the spring of the year which we call 431 BCE and which he called the first year of the war, and it continues into the late summer of the twenty-first year of the war (411 BCE), a war which he says was almost exactly 27 years long (for these facts see Thucydides 2.2, 5.25, and 8.60). It is likely that some of his contemporaries had also written histories of those years, but these do not survive: later historians chose to continue his account or to summarize and adapt it. Stories about the war must change sources at the point where his history ends.
Some decades later, Xenophon the Athenian decided to carry the story from the end of Thucydides’ narrative to the surrender of Athens. He wasn’t particularly concerned with exact dates, and they were probably difficult to determine by the time when he wrote, but he tried to report events in order and indicate the start of each campaigning season. Unfortunately, he forgot to indicate the start of one summer and one winter, dividing his story into six years one of which overlaps with the last year of Thucydides. Twenty years narrated only by Thucydides, one narrated by him and Xenophon, and five years narrated only by Xenophon makes 26 years, yet the start and end of the war were 27 years apart.
More time passed. Copyists glossed Xenophon’s history with notes on events which he had left out and tried to fit his years onto their favourite calendar. Their attempts to date Xenophon’s years according to the Athenian calendar, Olympiads, and years of the war just made the problem worse. Another ancient tradition solved the problem by inserting a year between the end of Thucydides and the beginning of Xenophon, producing the correct total of 27 years (21+6) but implying that Xenophon made a very serious mistake about when to start his story. Diodorus Siculus chose this solution for his history. It is curious that he needed to do so, since he trusted sources who were independent from Xenophon and unlikely to make the same mistake, but he used a seperate chronicle to help fit his narrative sources to a consistent calendar, and perhaps this chronicle followed Xenophon.
I know of four main guesses about where the missing year is. The first approach is to follow Diodorus and postulate a gap of a year between the end of Thucydides and the beginning of Xenophon. This is not popular amongst modern scholars. A second approach inserts the year into Xenophon’s second campaign season (Xen. Hell. 1.2) by postulating a year’s delay after the Battle of Cyzicus and before the Athenian attack on Ephesus during which the Athenians raised money and attacked small places. This theory was developed at the beginning of the twentieth century and seems out of favour. A third approach, proposed by Noel Robertson in 1980, adds a year between Cyrus’ arrival in Lydia and Alcibiades’ return to Athens (Xen. Hell. 1.4) by assuming that Alcibiades needed quite a long time to raise a hundred talents in Caria and that Cyrus really did hide his arrival for some time. A fourth approach inserts the year between Alcibiades’ return to Ionia at the head of an Athenian expedition and the naval battle at Notium which caused Athens to reject Alcibiades for the last time (Xen. Hell. 1.5.10) by assuming that a period when the Spartan fleet was pulled ashore to rest lasted many months. This theory is also about a century old and seems to be the most popular, being used by such writers as Jona Lendering and, I believe, Donald Kagan as well as the notes to the Penguin edition of Xenophon’s Hellenica. Advocates of each theory assume that some events took longer than they appear to in Xenophon, and try to use deduction or odd references in other sources to fill out the events of that year.
Choosing between these solutions, or proposing an alternative, is a difficult technical problem. Readers interested in the details can see academic works such as the Cambridge Ancient History or Noel Robertson’s article “The Sequence of Events in the Aegean in 408/407 BC.” http://www.jstor.org/stable/4435721 At present I have no opinion since I do not feel that I understand the problem well enough. But students of Greek history should be suspicious of any date between 411 and 405 BCE and should pay attention to where modern writers chose to insert a year. Juggling uncertainties and possibilities is one of the joys and tortures of studying ancient history.