In his account of the early years of the Peloponnesian War, Thucydides laments the way that the enormous expenses of the war were exhausting Athenian coffers. From the details of his complaint, we learn that every hoplite in an Athenian expeditionary army was expected to have a servant with him:

It was this, with Potidaia, that most exhausted her revenues, since Potidaia was besieged by a force of hoplites - each drawing two drachmai a day, one for himself and another for his servant.

-- Thuc. 3.17.3

In his earlier work, Herodotos already made the same assumption. He arrived at the size of the Greek army facing the Persians at Plataia by counting the number of hoplites, and then simply doubling the number. While any light-armed troops in the army probably weren't so fortunate as to have someone to do their chores for them, it was taken for granted in the case of hoplites. Needless to say, cavalrymen were expected to have even more staff along for the ride.

The main task of these servants - some of whom may have been dependants or even junior family members, but mostly enslaved people - was to carry the hoplite's stuff. Arms and armour were only a part of the load. Greek armies had no central logistics infrastructure or quartermasters; it was the responsibility of each man to bring or buy his own food, plus the gear to cook it with. And it was his servant's job to carry, prepare, and cook.

The servant's most important tool on campaign was his handmill. There is practically no evidence that the Classical Greeks used rotary grain mills (though they used rotary mills for other things), so we should probably imagine their handmills as basic stone mortar-and-pestle affairs. The servant would use this handmill every day to grind grain into flour to bake bread. This was the basic staple of the Ancient Greek diet, both at home and on campaign. The luxury grain at the time was wheat, but on campaign most Greeks would likely make do with the basic stuff: barley, baked into cakes or mixed into sticky porridge.

Baking, of course, required fire. This was a basic necessity for all armies. Xenophon tells us of a Spartan advance guard stuck on an exposed ridge in a sudden hailstorm, and how their spirits were lifted when their general had fire brought to them in great pots, so they could get warm and make food (Hellenika 4.5.4). Cunning generals could, of course, also take advantage of the times when enemy armies were scattered to gather firewood for their cooking fires.

With their bread, the Greeks would eat some form of opson - the savoury part of the meal. Normally this could involve meat or fish, but with no way to keep food fresh on the march, they had to rely on things that lasted. This mostly meant cheese, onions and salted goods. Aristophanes jokes that Peace smells of fruit and festivals, but the smell of war is the smell of onions, in soldiers' knapsacks and on soldiers' breath (Peace 527-9).

This stark diet could always be supplemented by anything the army could plunder along the way, if they were marching through enemy territory. Xenophon tells a famous story about how his men found stores of honey in an abandoned village in Cappadocia which turned out to be dangerously intoxicating and knocked them out for a day (modern scholars have gathered that this was probably honey produced from the nectar of yellow rhodondendron, which grows in the region in question and has this effect).

With their food, of course, the Greeks would drink wine. This was the standard drink; it was convenient for armies on the march, since it doesn't spoil and can be easily mixed with water from any available source. The wine would probably be kept in earthenware jugs. If there were no mixing bowls available, it would have to be poured out in small doses and mixed in the warrior's cup. If wine could be plundered, it could make life on campaign a great deal more pleasant. We are told that the Spartan mercenaries who invaded Corfu in the 370s BC found so much wine in the villages of the island that they became wine snobs and would reject anything that did not have a fine bouquet (Hellenika 6.2.6).