Understanding the Timber Wall.
- The precise pattern position of the postholes found in several recent excavations. 
- How the Romans were able to build a stone wall and forts in potentially hostile territory over a number of years dispersed along a 73 mile /120 km front.
- The context of the Turf Wall
- The position, form, and course of the ditch
- The width of the berm . . . Note; Per Lineam Valli – Mike Bishop's excellent and detailed guide to remains of the Wall, did me the honour of mentioning my work in this context.
The berm pits are not universally accepted as evidence of an entanglement. One writer has suggested that they are no such thing and in fact represent an early timber predecessor to Hadrian’s Wall. An interesting idea, but the absence of a berm between this putative timber wall and the ditch would make it unlikely on the grounds of stability, …
- The idea that the width of berm, wider than the Wall was tall, is for structural stability is an old but patently unfounded idea, inconsistent both with Roman practice elsewhere such as the Turf Wall, and a modern understanding of soil mechanics.
- Similarly, the idea that the large roughly circular postholes, up to 600 per 100m, could have held thorn trees with interlocking branches  is inconsistent with morphology of native trees and completely unrealistic in terms of arboriculture.
- These postholes have nothing to do with the branches and tree trunks buried in a backfilled ditch hundreds of feet from the Roman line [Cippi ] during the Siege of Alesia mentioned once by Caesar .
- However, they fit perfectly with the building of timber ramparts with a ditch in front, mentioned Caesar on numerous occasions, described by other authors, and which might be regarded as standard practice for the Roman army.
- The Roman army always dug in using earth and timber 
- You cannot defend a stone fortification while it is under construction.
- Therefore for every stone fort there must be a temporary timber and earth fort to house the work force and garrison.
- In addition, since the construction force was larger than the eventual garrison, temporary works may be more extensive than those of the finished frontier.
- Since gateways in forts and mile castles are the most technical aspects of the main Wall, the skilled legionary labour, working westwards, was probably spread out to mile castle level over quite long stretches simultaneously. 
- It would seem likely for the sake of logistics that there were smaller camps to house those garrisoning and building the sectors of wall between the main forts.
- After the first few seasons, a temporary frontier of earth and timber had been established, with fortifications housing the garrison of Auxiliaries as well and the legionaries, who working west, had built much of the "Broad" Stone Wall as far as the North Tyne.
- The construction of the wall has reached the central sector, [the only section where both the stone and earth forts and Wall now survive].
- Some scholars now think it likely that work on the wall was disrupted, probably by War. 
- When work resumed, probably after several years, the both quantity and quality of the work is scaled back.
- Then, almost as soon as the Wall is finished, it is abandoned in favour of a shorter more concentrated frontier further north. [The Antonine Wall].
- The Stone Wall fortifications were not yet finished.
- There is good cover in rough uneven terrain to North of Wall.
- Might catch a legionary force spread out in work details.
- The Region is furthest from the coast – from where reinforcements can be brought in by sea.
- Splits the Roman forces in half.
- Hold the high ground in the centre with options to move south on either flank of the Pennines.
- From the Roman point of view the forces along the frontier are now dispersed and facing the wrong way.
- The two land routes reinforcement can come from York or Chester, both can be out flanked by a force in the centre
- It is also worth noting that the east central sector was reinforced with extra forts when work resumed after the dislocation, [the fort at Carrawbrough/ Brocolitia below].
Sources & further reading
Note; This article uses illustrations based on images from Google Earth: ttp://www.google.com/earth/index.html [Accessed 07/12/11]