Caesar\'s Self-Propelled Siege Tower

[D B Campbell]

An article in the book mentions Caesar's usage of siege towers that are moved with no apparent power source. Writers' claim is that it is certain some kind of mechanism used for powering wheels from inside of tower.

This is a 2010 article entitled "Ancient motors for siege towers" by C. Rossi, F. Russo & S. Pagano. The first of these three names automatically rings alarm bells in my mind. In the past, he has been responsible for some claims that I find surprising and sensationalist (e.g. that Archimedes used steam-driven cannons). He rarely cites sources and seems to rely chiefly upon his imagination (I should add "in my opinion", so as not to offend anyone).

It is a pity that the three authors do not cite any previous scholars who have addressed the problem of moving a siege tower. It is clear that they have read some of them, because their first two schemes are lifted (without acknowledgement) from Marsden and Schramm. Yet, rather than credit these scholars, they pass the designs off as their own (e.g. "Fig. 3. Authors' pictorial reconstruction of the propulsion by capstans" is a coloured-in version of Marsden 1971, p. 87 fig. 3; "Fig. 5 Pictorial reconstruction of tread wheels" is an obvious borrowing from Schramm & Rehm's edition of Biton).

In fact, if they had consulted the excellent 1983 book by Otto Lendle (Texte und Untersuchungen zum technischen Bereich der antiken Poliorketik -- this is basic required reading for anyone interested in siege machinery), they would have seen that both methods have been critiqued and found to be unlikely.

Yet, I think it is also quite possible to push siege towers within by placing enough human power.

You are quite right. Lendle drew attention to the design of the undercarriage of these machines -- unfortunately, our Italian colleagues do not get into this degree of analysis. In fact, they don't analyse the design of the siege tower at all! The bases of the larger siege machines all incorporated rows of closely spaced crossbeams, between which dozens of men could be deployed as a human source of propulsion.

In my 2003 book Greek and Roman Siege Machinery, pp. 12-13, I discussed another possible method of propulsion. For the truly gigantic helepoleis, I suggested adapting a method first illustrated (afaik) by Chevalier de Folard, whereby the power source (whether animal or mechanical) is situation some way behind the helepolis, and propels it forwards by means of pulleys acting on anchor points concealed beneath the front of the helepolis; as the helepolis advances, the anchor points are periodically moved forwards, but always concealed beneath the gigantic frame of the vehicle so as to be protected from sabotage.

Russo and his colleagues state that "Some possible reconstructions of motors that could have been used for the helepolis’ motion were examined", before concluding that "Among these, the one that seems more suitable and effective is the counterweight motor." They are mistaken. (In my opinion, of course.)

I am wryly amused by their final statement, that "this also is an example that shows how, in order to correctly understand the past, it is necessary a wider cooperation between scholars having humanistic knowledge and scholars having technical knowledge." Or maybe just read the relevant literature? :wink: