Anabasis XII

The lack of cavalry tells on the first day, in which the Persians send cavalry to spy upon and then harass the Greeks. The mounted bowmen and slingers that the Persians employ inflict significant damage on the rear guard during the march to the villages. Xenophon decides to break formation and charge them, but on foot his men cannot reach the enemy before they can withdraw; and the Persian archers (raised to 'shoot straight and speak the truth') are pretty good shots even while retreating. 

The Greeks reach the villages they mean to plunder, and spend some time refitting some of their pack horses as cavalry mounts. They identify about fifty men who are fit to serve as cavalry, and also some slingers, in order to disrupt future such attempts by the Persians who are following them. 

The Persians return with a thousand cavalry instead of a few hundred, but the Greeks have crossed a ravine before they arrive. The new Greek force is able to deploy against the Persians during their own crossing, striking the vanguard and driving it into retreat. They kill a few Persians and mutilate the bodies to make clear that they're not interested in playing nice any more. 

After this the Ten Thousand march through a set of ruins of cities and fortresses where the Medes -- the same ones who provoked the building of the Median Wall -- had been contesting the area with the Persians during their short-lived empire. Tissaphernes arrives with a very large force, but he shows the typical Persian desire not to risk any lives in the fighting, so he tries to bombard them again. Their new force repels him successfully with disciplined and accurate return fire from the slingers.

The Ten Thousand begin to recover enemy bows and arrows, which are different from the ones they knew at home but which they are able to employ successfully. They also discover in their raids of villages additional bowstrings and lead that can be cast into bullets. Their slingers prove to be better than the Persian ones, having a longer range. The Persians continue to follow, but they are having the worst of the skirmishes.

The hollow square formation, which again is novel I think in this era, proves to have some practical difficulties for traversing bridges, valleys, etc. The Greek generals begin making adaptations on the fly to address these difficulties: 

The generals accordingly, having recognsied the defect, set about curing it. To do so, they made six lochi, or divisions of a hundred men apiece, each of which had its own set of captains and under-officers in command of half and quarter companies. It was the duty of these new companies, during a march, whenever the flanks needed to close in, to fall back to the rear, so as to disencumber the wings. This they did by wheeling clear of them. When the sides of the oblong again extended, they filled up the interstices, if the gap were narrow, by columns of companies, if broader, by columns of half-companies, or, if broader still, by columns of quarter-companies, so that the space between was always filled up. If again it were necessary to effect a passage by bridge or otherwise, there was no confusion, the several companies crossing in turns; or, if the occasion arose to form in line of battle, these companies came up to the front and fell in.

As they leave the plains and begin to rise into the hills they discover another problem, which is that their formation is easily attacked if the enemy is able to cover it from an elevated position. The first day this happens they suffer a large number of wounded among their light infantry. After this they make an additional modification and assign a division of the force to hold the heights while the bulk marches on the roads below. This is slow, though, as the heavy infantry so assigned have to struggle in their armor up to the hills and then along the crests. 

They have the advantage that the Persians do not wish to fight at night, being a large collection of strangers rather than a disciplined and unified force. Thus, the Persian cavalry withdraws each night some miles away to camp, catching up to raid the Greeks the next day. The Greeks begin just occupying villages during the fighting hours, so that their superior marksmanship can tell on the Persians; then they begin marching at night after the Persians withdraw, gaining a few days of peace in this way.

On the fourth day of this strategy, however, the Persians force march themselves to a mountain overnight and occupy the heights of one of its arms, which the Greeks have to pass. Xenophon leads a charge up the heights of the arm, which the Persians abandon to retreat to the summit: they do not wish to come to direct blows with the heavy infantry. The climb is very difficult for the hoplites, but they eventually win the summit as well, the Persians withdrawing before them. 

The Persians now switch tactics as well. They have learned that they cannot win against the Greeks in a stand up fight -- they have superior numbers and combined arms, but lack the unity and morale. Thus, they switch to the extraordinary remedy of burning their own Persian villages in advance of the Greeks, in the hope of starving the Greek army.