Mark S. Thompson is a military historian who has been studying the Peninsular War for around 40 years. In 2009 he completed a PhD on the role of the Royal Engineers in that conflict, published under the title 'Wellington's Engineers'. He has published several books and papers and frequently participates in conferences, both in the UK and abroad. He is a member of the British Commission for Military History, the Friends of the Lines of Torres Vedras, the Friends of the British Military Cemetery at Elvas, the Society for Army Historical Research, the Waterloo Association, the Napoleonic and Revolutionary War Graves Charity, and the Royal Engineers Historical Society. We spoke to Mark about his latest book, 'Wellington and the Lines of Torres Vedras: The defence of Portugal during the Peninsular War, 1807-1814'.
Reading your book, one can tell that the project of the Lines of Torres Vedras had everything to go wrong. Why did it succeed? What was the moment and circumstance when it was truly realised that fortune had smiled on the Allies? In other words, can the success of the Allied army and the Lines be attributed to a particular decision or a specific event?
The construction of the Lines commenced in November 1809. The original orders did not detail the design of the forts. Wellington, having ridden over the area, identified the locations that needed defences and the engineer officers examined the locations and decided what was required in each position. Wellington had lived near Torres Vedras in 1808 and will have ridden the hills in the area. I am sure Wellington will have seen Neves Costa’s report and this will have helped him to identify the critical locations.
It must be remembered that the original construction work was done quickly with Wellington knowing that a rapid French advance could arrive in front of the Lines as early as Spring 1810. As we now know, Wellington was given an extra six months and this allowed the initial defences to be extended and improved.
There were adjustments to the original plan as the engineers understood what could be achieved e.g. the decision to abandon the area around Castanheira and move the Lines back to Alhandra or the decision to extend the defences around São Julião (St Julian)
The French officers and soldiers would have been demoralised when they saw the Lines. Both were expecting to move into comfortable winter quarters in Lisbon.
I am not sure that there was any specific decision that was critical, it was the scale of the works that disheartened the French. From their positions, they could see the extensive defences on what we now call the First and Second Lines. The French knew they would suffer terrible casualties attacking the Lines and possibly would then not be strong enough to take and hold Lisbon.
There were a number of probing attacks soon after the French arrived in front of the Lines, particularly at Alhandra and Sobral. After this the French settled into a blockade and there appeared to be no intention of further attacks on the Lines.
The moment when Wellington realised the Lines of Torres had worked would have been on the foggy morning of 15 November when it was reported that Masséna’s troops had withdrawn, establishing themselves around Santarém.
For those who have become accustomed to today's instant communication, it is perhaps difficult to understand how armies could be commanded with such a lack of information. It's almost possible to follow your account of Masséna's movements as if it were a detective novel. The secrecy to which the construction of the Lines was subjected also seems unbelievable today. In war as in civil society, what creates more fake news: too much information or the lack of it?
Even in the early 19 Century, generals would have expected to have maps available for countries they were invading. There is much criticism of Masséna’s lack of maps although recent research suggests that he had better maps that many historians suggest. An army advancing into enemy territory would have usually sent out scouts. Due to the brutal guerrilla war, the French were unable to do this without sending out large bodies of men. With Masséna were Portuguese officers who would have some knowledge of the country and also French officers who had been there before (e.g. Junot).
The secrecy of the building of the Lines is an interesting question. There is much information to suggest they were not a secret. Many British officers commented on the building of defences. Masséna was aware of the defensive work well before he arrived in front of the Lines. In both cases, it was the scale of the work which was not understood. A British officer travelling up the Tagus, might see the defences around Alhandra. But he would not know that there was a line of forts stretching West to the Atlantic Ocean. Masséna believed that he would be able to force his way through or around the defences.
Information / disinformation was as much a problem then as today. Without satellites, drones or maps, information came in slowly and was often based on someone’s opinion rather that fact. The skill was in filtering the information to find truth or fact. The lack of information was always a problem as people tried to fill the gaps with guesswork. You needed to know the source of the information to be able to decide on its accuracy.
On the Lines, Wellington had a telegraph system built to allow rapid communication. With up-to-date information, Wellington could quickly move his troops to where they were needed.
Kandinsky used to say that “everything begins with a point”. For Paul Klee, a line was “a dot that went for a walk”. It’s not difficult to transfer this graphic idea to the Lines and their forts, which are at their best when, seen from the air, they take on all the beauty of their geometry. Was there any passion and creativity, or was it just a matter of following rigid rules in a pragmatic way? Did a military engineer see the Lines of Torres Vedras differently from everyone else?
Access to aerial information has been a huge boost for historians and archaeologists. Aerial and satellite information have allowed us to see structures that are not visible from the ground. Drone technology has allowed us to get much closer to the subjects. We now also have LIDAR and ground penetrating radar that allow us to see what is under the ground. As an example, using LIDAR the trenches used at the siege of Ciudad Rodrigo in 1812 are still clearly visible.
The design of the Lines cannot really be seen as a work of art. It was much more practical. A fort was placed in a position to stop enemy access to a high point or a route through the Lines. Its structure was determined by what it needed to defend and the shape of the ground on which it was to be built.
When we look we see a pretty hill, or river or valley. A military engineer will see a hill as a high point for observation and to command the lower ground around it. He will see a river as a barrier or something that needs to be crossed by bridge or ford. A road will aid movement or hinder movement if it is destroyed. A forest is something to hide movement or to be removed to help with observation. It is a very bleak view of the countryside.
In recent years, a strong communal effort is being made to preserve what still exists and recover what had virtually disappeared from the Lines, from stone structures to the most fragile earthworks. At the same time, a vast region in the centre of Portugal is turning them into an axis of identity and a project for the future. Is there awareness in Britain of this development?
The challenge for the Lines of Torres is that battlefields attract the most attention from those interested in military history. Sieges and defences are less interesting. There is limited knowledge in Britain of the developments on the Lines and in the wider Iberian Peninsula. Groups like the ‘Friends of the Lines of Torres Vedras’ aim to promote the Lines and those who care for them. There have been a number of books on the Lines in English over the last twenty years (including mine) that also highlight the existence and importance of the Lines.
Looking forward we need to look at how we can assist in promotion of these new programmes in Britain.
Precarious structures on the ground, built to last as long as Masséna’s troops sieged them – according to your book, many of them were reinforced with stone just to withstand the violence of the climate during that period – are resurfacing today, with a vigour that seems to promise to last for at least another two centuries. What was temporary two hundred years ago has now become permanent. Does this surprise you?
Yes, it does. Earthworks by their construction are meant to be temporary structures. It is amazing to think that 200 years later, we can still walk in a ditch that has lain untouched for this time. I hope that new technologies, like LIDAR, will encourage further work to preserve what is still there but hidden. It brings a greater urgency when you can see it.
Even in the last few years I have seen evidence of walls collapsing in maintained forts due to the weather in winter. To last another 200 years will require continuous maintenance.
The preservation of many of the forts is probably due to the fact that they are in inaccessible places. I live near Hadrian’s Wall in England, and many of the stones from the wall are spread for many kilometres in every direction to make farm walls! We need to keep sheep in the fields in England. Olive trees and vines do not need fences!
And would it surprise Wellington?
Yes, I think it would. The defences were never meant to last longer than the need for them. The forts required constant maintenance from 1810 to 1814 and I am sure will have degraded quickly after the war. The forts will have left Wellington’s memory long before they disappeared on the ground.
Is there still much to discover about the Lines of Torres Vedras?
There certainly is. On my last visit in 2022, I spent some time trying to visit some more remote forts (e.g. forts 76, 78 & 80). I many cases, I failed. I think that there are still opportunities to clear and survey some of these sites. There are some where it is difficult to access them due to the state of the roads (e.g. forts 9, 12 & 13). The biggest threat at the moment is business or industry damaging sites, not realising or caring about their historical importance.
The comments above are not meant to criticise the amazing work done by the local municipalities, the CILT and its predecessors. Since I first visited twenty years ago, there has been an unbelievable improvement in the care of, and access to, the locations on the Lines of Torres. The many Interpretation Centres across the Lines make it possible to understand this vast project. Portugal, you should be proud of what you have achieved.
