The stratagem of the oxen permits the first examination of the possible size of the Carthaginian army. Here is the start of employing known factors and probability against the historical literature of the period.

Moving the elephants across the Rhone River. Hard working Carthaginians knew something about difficult movement.

"He [Hannibal] sent for Hasdrubal, who was in command of the army's pioneers, and ordered him to have as many faggots as possible of dry wood made up with all speed, to select from the plundered herds some 2,000 of the strongest plough oxen, and to mass them in front of the camp. With this done he assembled the pioneers and showed them a ridge which was situated behind his camp, and the pass by which he intended to march. When they received the order, they were to drive the oxen towards this high ground as fast and as furiously as they could until they reached the top. Next he ordered the whole army to take their evening meal and to retire to rest early. Towards the end of the third watch of the night he lead the pioneers out of the camp and ordered them to fasten the faggots to the homs of the oxen. There were plenty of men available and the task was quickly carried out, after which he ordered them to light all the faggots and drive the oxen up to the ridge. The light armed pikemen, who were stationed immediately behind, were ordered to help the drivers for a certain distance up the slope. Once the animals were well on the move, the soldiers should run along behind them and keep them together as they made for higher ground. They were then to occupy the ridge, so that if the Romans advanced on any part of it, they should engage and attack them. At the same time Hannibal himself made off with his main body towards the narrow entrance of the pass; his order of march consisting of the heavy infantry in front, next the cavalry, then the captured herds, and finally the Spanish and Celts." [Polybios, Book 111, 93]

What we know from this account is that a night movement through a pass was accomplished for the body of the Carthaginian army sometime between late evening and early morning. As written by Polybios above, the movement did not begin until third watch. Livy, Book XXII, 17, stipulates this begins immediately after dark. Both accounts imply that the pass was cleared by the Carthaginian force before sunrise. If this event occurs around the end of August or early September, the time between sunset and sunrise will be approximately 11 hours at 40 degrees latitude. Additional to the consideration of simple sunrise and sunset is the condition known as twilight. That is the time between sunset and total darkness or total darkness and sunrise. The execution of a such a military operation must include the calculation of twilight or risk losing the surprise advantage that darkness provides. For general consideration in this article, a period of 40 minutes is employed for twilight. This provides a working parameter of 9 hours and 40 minutes if the start is based upon Livy stipulation of the commencement of the movement. The time available diminishes significantly if Polybios' account is accredited. Regressing to Hans Delbruk's 30,000 man army corps, the length of such a formation with relatively modern roads and contemporary march formation discipline, was 14 miles long. While this corps had artillery trains, it lacked both the train of booty and herds encumbering the Carthaginians. Extrapolating the length for a force of 50,000, a formation with similar march discipline would stretch a little over 23 miles. A formation without the march discipline would obviously stretch even further. It would be highly improbable that the Celtic portion of Hannibal's force would have the formation integrity exhibited by Delbruck's example military formation.

A road march for a large column of troops will be between 3 and 2 1/2 miles per hour in daylight [Engels, Donald W, Alexander the Great and the Logistics of the Macedonian Army, Notes on Table 7 and the author's experience with modern military road marches executed from 1985 through 1986 with the 10th Mountain Division, Light Infantry.] These are substantially the optimal speed for sustained march operations. While smaller formation can and have achieved higher rates of march, Engels work demonstrates the inverse relationship between size and speeds of military columns. The execution of a night march introduces additional conditions which degrades even these rates. The darkness which conceals the Carthaginian column also denies it the clear visibility of the quality of the footing, the navigational landmarks, and clear verification of identity and integrity of the formation in front of it. In order for the ruse of the oxen to work, the lighting to assist in movement had to be greatly diminished. The flames on the homs of the oxen could not outshine the torches carried by thousands of men clearly aligned in one long road column.

The Carthaginian force therefore did not carry significant means of additional lighting in the execution of the march. With minimum visibility, elements within the column would not have a visual measure of the speed of the formation in front. This results in an accordion effect. This is where one element speeds up and runs into the rear of the preceding element. That in turn causes the faster moving element to slow down if not halt. The image best understood by modern -readers is the classical bottleneck on a freeway. Someone slows down in a curve and everyone behind begins to brake. The effect can back up for miles. We've all been there at some time. It obviously degrades the overall flow of the traffic at any specified speed and we all know where we're headed.

Beyond the mouth of the pass away from the Romans, the destination was not so certain. In his movement to the Campania region through this land he has already transited, Hannibal had already found himself lost [Livy Book X)UL 13]. Now his army was moving at night upon roads he had been denied access to since entering the territory. Land navigation at night even on unimproved, by 20/21st century standards, roads is a circumspect action. The shadows of the hills and mountains, the lights of villages, the flow of rivers, and the shine of the stars are the only real guides. In the darkness, road intersections without markings and water crossings induce hesitation and delay. Additionally, the rates of march employed by Engels are with formations constituted of men 10 abreast and cavalry 5 abreast. Any portion of the pass which further constricts that width, further retards the speed of the entire column. Again, the modern example are those instances on the freeway where suddenly the number of lanes change from 4 to 3 and then 3 to 2. We've all experienced the backup and drop in speed that incurs. All these aspects further degrades march speed.

Notice in Polybios' description of the order of march of the column, Hannibal has placed his most valued and reliable elements, those of his heavy infantry and cavalry first. The Spanish and, finally, the Celts bringing up the rear. The elements in the van are the ones must likely to maintain both march discipline and integrity. The latter the least likely. This is different from their march from the River Trebia to Lake Trasimeme when the Spanish and African veterans were in the van, the Gauls in the middle, and the cavalry in the rear, more to insure the Celts didn't leave the army [Livy XXII, 2]. Deep in enemy territory and confronted with an untenable operational situation, Celtic desertions are unlikely. However, the tendency for the march column to elongate is now greater. It will take a good portion of the evening before these elements are even exiting their bivouac or camp. However, their lack of discipline and integrity will not have an immediate adverse effect on the speed of the column that has departed before them.

More History of Logistics: Part One

Background and Prelude
Night of the Oxen
Comparative Rates of March
Feeding an Army

History of Logistics: Part Two

Returning to the Scene of the Action
Sustaining an Army
Supply, Size, and Tactics
The Writing of History