Aeneas Tacticus 18.1-12, 18.21, 20.1-2: Locking the Gate; sabotage of gates and locks

How to make sure that the gate is locked securely at night, and no-one is able to tamper with the lock. Gates are shut with a crossbar on the inside, which is then locked with an iron bolt.






18. [Closing the Gates]

1. When those who come in from the country are within the city and evening is coming on, the signals should be given for dinner and for mounting guard. While the guards are getting ready, you should inspect the gates to see that they are shut fast; for disasters are very apt to result from the magistrates slackness in regard to bolts. 2. If a magistrate does not attend in person to the duty of bolting the gates, but delegate it to the sentinel, tricks can be played by the sentinel who wishes to let in the enemy by night. I will give examples.
3. One of them poured sand into the socket in the day-time, so that the bolt should remain outside instead of slipping down into the hole. Even bolts already in position are said to have been undone by pouring sand gradually into the socket, 4. and working the bolt to and fro noiselessly, so as to avoid notice, until, as the sand fell in, the bolt was gradually lifted and could easily be taken out. 5. Once, too, a gatekeeper who had been deputed by his general to fasten the bolt, stealthily cut a notch into it with a chisel or file, tied a knot of string round it, pushed home the bolt, and, after waiting a short time, pulled it up again by the string. 6. Another prepared a fine net with a string attached, pushed home the bolt enclosed in the net, and afterwards drew it up. The bolt has also been removed by being knocked upwards. Again, it has been taken out with a small pair of pincers: one nipper of the pincers must be hollowed like a channel, the other flat, so that you can receive the bolt with the channelled pincer and get a hold upon it with the other. 7. Another traitor succeeded in turning round the cross-bar without being noticed, when he was about to insert the bolt, so that it could not fall into its socket, and the gate could be opened afterwards with a push.
8. At a city in the district of Achaea, where they were plotting secretly to let in mercenaries, their first step was to take the measurements of the bolt in the following manner. 9. They inserted into the socket during the daytime a loop of fine strong string, with ends projecting but concealed; and when the bolt was inserted at night they pulled it up, along with the loop, by pulling the ends of the string, took its measurements and replaced it in the socket. Their next step was to get a key made to those measurements, which they did as follows. 10. They had a tube and a rush-mat needle forged: the tube was of the usual pattern, as was the greater part of the needle, including the sharp end; but its handle was made hollow, like the hole in a spike where the shaft is inserted. 11. A shaft was put in at the smithy, but taken out when they carried it home, so that the needle could be driven against the bolt and made to grip. The trick played to get the instruments made without the smith's suspecting the object for which he had made them was certainly a very clever one.
12. Once, too, the circumference of the bolt was measured, while it was in the socket, in the following way. Potter's clay wrapped in fine linen was inserted and pressed down with a tool round the bolt; then the clay was pulled up, an impression of the bolt taken, and a key made to fit it.
21. In view of these various devices no precaution must be omitted: the magistrate must shut the gate in person, and not give the bolt to anyone else.


20. The Prevention of Tampering with Bars and Bolts

1. To prevent any tricks being played with these, a general should, first of all, go in person to shut the gates and make his inspection, before he has dined, and not entrust anyone else with the task when he is disposed to be lazy; in time of war he will need to have all his wits about him in the performance of his duty. 2. Secondly, the bar should be covered throughout its whole length with three or four thicknesses of iron, so that it cannot be sawn through. Thirdly, three bolts of different patterns may be put in on different days: one of these should be kept by each general; or if the generals should be too many in number, their days for this duty must be decided by lot. 3. And it is best to have the bolts not removable, but held down by an iron place, so that when the bolt is being taken out, it may never be lifted by the pincers higher than will enable it to be inside the bar while the gates are being shut or opened. The pincers must be so made as to slip under the plate and lift the bolt without trouble.






Aeneas' main concern in this extract is the bolt (balanos), which served as the main locking mechanism for a Greek city gate. The gate, with its two leaves opening inwards, would first be secured with a cross-bar on the inside, which was fastened in sockets on either side of the gate. Then the bar was locked with the bolt, a round iron pin which was dropped through a hole in the bar into a socket in the wall beneath. The main security feature of this simple mechanism was that it was difficult to extract the pin through the bar from its socket. This could (at least in theory) only be done with a special key.

This passage makes it clear just how important it was to keep the gates secured: the main danger to a city under siege was that someone on the inside would be persuaded to open the gates at night.

Aeneas is clearly very concerned with preventing such treason, but at the same time, he displays a certain fascination with plots he considers particularly clever.




created 14/02/2010 - updated 14/02/2010