This Spartan delay in responding to an urgent summons has puzzled historians for almost two thousand years. Herodotus stated explicitly that "it was the ninth day of the month, and they [the Spartans] could not take the field until the moon was full," which most historians take to mean that Sparta was celebrating the Carneia and out of piety delayed deployment. Plato, however, claimed that the Spartans arrived too late for the Battle of Marathon because they were delayed by a helot revolt, an uncorroborated theory that has become very popular with modern historians. More recently, W. P Wallace in his article, “Kleomenes, Marathon, the Helots, and Arkadia,” (The Journal of Hellenic Studies, Vol. 74 (1954), pp. 32-35) suggests that King Cleomenes was creating so much anti-Spartan sentiment among the Arkadian cities that the Spartans could not risk deploying their army until King Cleomenes was back in Sparta. In my essay "The Importance of Marathon for Sparta -- and Leonidas," I argue that since the Spartan army was then always commanded by one of her kings and King Cleomenes was either in Arkadia or mad and King Leotychidas was either still on Aegina or discredited that the Spartans needed to select a non-royal commander which in turn required the approval of the Spartan Assembly -- a procedure that took (a finite and predictable amount of) time. (I.e. "after the full moon.")
Yet the bottom line is that all these theories – helot uprising, Arkadian discontent, or a crisis in command – are essentially the product of dissatisfaction with the explanation provided by Herodotus: a religious festival. Before we reach for alternative explanations, however, we ought to admit to ourselves that we know very little about Spartan religious festivals. Most especially, we do not how they affected the readiness of the Spartan army. The assumption that a religious festival might delay departure of the army simply because of pious scruples may be entirely wrong.
What if, for example, the Spartan Army was given leave during religious festivals, or reduced to a skeleton of “duty officers” for each unit? It is certainly normal for religious festivals, in all cultures over all times, to be family occasions. Why should Sparta have been any different? The very fact that there is no mention of how “odd” the Spartans were in this regard suggests that their behavior was conform to other Greeks and elicited no comment.
A family holiday in Sparta might have implied that even the young men were exempt from sleeping in barracks and all men exempt from dining at their messes. Again, the fact that this is not explicitly mentioned is no evidence that it is not possible. There is no mention of men being exempt from duty and collective dining to participate in the Olympic Games either, but Spartan athletes were very prominent at the Olympics and they had to train in Elis for a month before the events just like all the other competitors. Likewise, Spartan spectators at the Games could not be eating and sleeping in Sparta while they were at Olympia. In short, the rules about living in barracks and eating at the messes where for “ordinary” days. The Olympics, war, and, arguably, religious festivals would have been “extraordinary” or “exceptional” days.
We know, further, that Spartans all had at least one state kleros, and that wealthier Spartans had more extensive estates. Without knowing the yield of an acre of land using 5th Century agricultural methods, I have no way of estimating just how large a kleros had to be to support a man and his family, and without knowing how large a kleros had to be, I cannot estimate how many could have been located within easy walking/riding distance of Sparta’s barracks and messes. However, I think it is fair to say that not all 8,000 – 9,000 kleroi could have been within a couple-hours reach of the heart of Sparta. It is far more likely, that many kleros were more than a half-day, even a day or two, away from Sparta. Some may even have been located in Messenia, on the far side of Taygetos, or on Kythera. Reaching these estates to check up on things, and to collect rents, would have taken Spartans away from Sparta for days on end.
The requirement to be present in Sparta most of the time, meant that most of the time the estates were left in the hands of helots, perioikoi overseers or wives. Yet the fact that Spartiates were absent from their estates most of the time only reinforces the need to be present some of the time. Particularly if Spartiate/Helot relations were as bad as most people make them out to be, no Spartan could afford to leave his kleros entirely in the hands of his helots or even perioikoi overseers. It would have been necessary for Spartiate landlords to periodically visit their estates in order to ensure nothing was so mismanaged as to endanger payment of his syssitia and, if he had sons, agoge fees. If a kleros was left to a wife, the desire to visit periodically would have been even greater, particularly if there were young children with her.
In short, Spariates would have periodically travelled to their distant kleros and while doing so they would have been excused both from their military duties and exempted from eating at their syssitia. Probably, any man could apply for leave to go to his estates whenever it suited him. Possibly, it was traditional for men to go to their estates during holidays, when men were given leave to be with their families in any case.
For the wealthier Spartiates from the so-called “better” families, the 400-500 families that made up Sparta’s elite, the need to visit estates would have been even more acute than for the poorest with only one kleros. The elite would have had multiple estates to look after, horse-farms, kennels, orchards etc. They would have needed to be away from Sparta even more often than the poor. And it was this elite that, at least in the later years of the 5th Century, occupied most of the positions of authority, power and command in the Spartan state and army.
What this means is that Pheidippides may have arrived in Sparta when the entire Spartan army was dispersed and the commanders scattered about Lacedaemon on their distant estates. The ephors would have needed to recall at least the members of the Gerousia and the officers of the army as well as cancel leave for those units they wanted to send to the aid of Athens. The ephors could, I suspect, calculate pretty accurately how long it would take messengers to reach the lochagoi and other senior officers, and how long they would need call up their troops and get them ready to march. That time frame alone – and nothing so impenetrable as piousness, helot revolts, foreign policy considerations, or even command uncertainties – might have determined the date the Spartan army marched out to Marathon.