The Fourth Crusade: new evidence challenges long-held opinions

The final results are in and Dr Andrew Blackler, project lead for the Dating of the Towers of Chalkida, Greece, reveals the surprising findings of the project we funded in 2022 to try and date the hundreds of towers in the region.

In the autumn of 1204 forces of the Fourth Crusade, fresh from their capture of Constantinople, annexed central Greece. Studies have been undertaken of the major fortifications they constructed, but little is known about the hundreds of towers, which are today a ubiquitous reminder to the modern tourist of the medieval period in the region.

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The traditional interpretation is that they were built by the incoming westerners- the minor nobility – as part of a process of colonisation, to display and impose their power over the local Greek population. Yet, since no scientific study has ever been undertaken, we could not even be sure when they were built, and therefore why they were constructed or by whom – until now.

Figure 1: Map of Central Greece with Survey area on the island of Evia (Euboea)
 and the towers sampled (inset)

Following a two-year research program, funded by the Castle Studies Trust and led by Andrew Blackler, a member of the five-year ‘Hinterland of Medieval Chalkida’ survey, surviving towers in central Greece have now been dated using modern laboratory techniques. In October 2022 a team, including technical staff from the Institute of Nanoscience and Nanotechnology ‘Demokritos’ in Athens and from the Ephorate of Antiquities in Chalkida, took samples of wood and mortar from seven surviving towers on the island of Evia (Euboea). This is the second largest in Greece and runs two hundred kilometres down its eastern seaboard. The island, just seventy kilometres north of Athens, is separated from the mainland by a narrow strait only thirty-nine metres wide, the tidal flows of which even Aristotle failed to solve! Chalkida, its capital, became the Venetian administrative centre (as Negroponte) of its Aegean possessions in 1390 and, following its capture by the Ottomans in 1470, their capital of Central Greece for 350 years until the formation of the modern Greek state.

Figure 2. The ruins of a typical tower (Mistros)image description

All of the towers (walls about 8 x 8 metres and height up to 18 metres) were in an advanced stage of collapse. Samples were taken of the wood inserted to provide internal lateral structural integrity to their walls, and of the mortar used to bind their rough stonework. This ensured that these materials were not part of a more recent repair or renovation, which would have been the case for beams used to support the multiple floors of the towers, but part of the original construction phase. The ten timber samples obtained were then subjected to a process of radiocarbon (14C) dating, whilst the mortar was analysed using optical and scanning electron microscopy (SEM) and other techniques (pXRF and XRD) at the Demokritos laboratory.

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The results have been exceptional. Six towers from different topographic locations (coastal, floodplain, mountain areas) have been dated with 95% certainty to a period between 1270 and 1434. Unfortunately, the accuracy for most samples was only approximately +/- fifty years due to fluctuations in the cosmic concentration of 14C in the earth’s atmosphere caused by solar activity during the fourteenth century: there were therefore two possible dating ranges identified. Two samples were of sufficient quality that, using what is known as ‘wiggle’ analysis, more accurate dating was obtained.

Figure 3. An example of one sample showing the wiggle in the calibration curve, that causes widening of the calibrated ages and splitting of the ranges.

The analysis of the mortar samples also demonstrated that two towers had two phases of construction. It is difficult to know whether this was a deliberate action or simply a reconstruction due to the collapse of the upper levels, given that the region is subject to frequent seismic activity. More importantly, since we could not identify any timber samples for one tower, it was possible to show that the chemical composition of this tower’s mortar was similar to two other towers in its immediate vicinity and thus was possibly also constructed in the fourteenth century.

The general conclusion, therefore, is that all the towers studied were probably built at least a century, or five generations, after the annexation of the region by western forces, and no towers were built immediately after the Crusaders took control. The ’colonial’ interpretation of their role is thus overturned or, at the least, requires reconsideration. Rather, their construction appears to have been a reaction by landowners to increasing instability in the region following invasion of the island by Byzantine forces in the 1270’s, the threat of attack by the mercenary Catalan Company who took control of Thebes and Athens in 1311, and a growing fear of seaborne assault by Turkish corsairs in the fourteenth century.

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Video updates on two 2022 Castle Studies Grants

Back in May the geophysical of survey took place at Pontefract Castle. Find out what they were surveying and the various techniques they were using to achieve the best results

You can find more about the different geophysical survey techniques in the article we published back in January 2021 by our geophysical survey specialist assessor Kayt Armstrong:

While here is a short taster video of a project yet to properly start – dating the towers of Chalkida in Greece. With permissions having been granted by the Greek government, Dr Andrew Blackler outlines what they will be doing when the fieldwork gets underway in September.

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Castle Studies Trust is going on its travels in 2022

In its latest round of grants the Castle Studies Trust has awarded £34,000 to five projects including two projects outside the UK. As well as covering a wide geographic area the projects will also undertake a broad range of technics to boost our understanding of castles.

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Dating medieval towers in the hinterland of Medieval Chalkida, Greece:

Stand-alone medieval towers, often part of castles or larger fortifications, are common in Central Greece. Often thought to have been built by the Frankish nobility during their period of dominance between 1204-1470, there is minimal evidence to back this up. By taking wood and mortar samples, the project aims to answer that question.

The present project forms part of the five-year survey ‘Beyond Chalkida: Landscape and Socio-Economic Transformations of its Hinterland from Byzantine to Ottoman times’ (authorised in July 2021 by the Greek State)

Samples will be taken from six towers of wood used laterally within tower walls to increase their structural strength, and mortar from within the core of the walls (both therefore probably

contemporaneous to the original period of construction). Specialists will use dendrochronological and

Carbon 14 methodology for the wood (8 samples), and optical microscopy, Scanning Electron Microscopy (SEM), and X-ray fluorescence (XRF) and diffraction (XRD) Spectroscopy (mortar – 21 samples).

Work will start at the earliest in late 2022 and may not actually take place until next year due to the time it is likely to take to get official permission from the government. 

Kilmacahill, Co. Westmeath

Geophysical survey of deserted medieval settlement close to Jamestown motte & bailey castle. The aim is to understand the morphology of settlement and its relationship with the castle and medieval monastery.

This survey will contribute to a larger project: the Human-Environmental Exchanges in the Landscapes of Medieval Ireland Project (HELM Project) which aims to use a combination of multispectral imaging, UAV drone survey along with geophysical survey to gain a much better understanding of the form of the deserted medieval village through non-invasive methods.

At time of writing it was unclear when the survey will take place.

Pontefract, West Yorkshire

Pontefract Castle: Service area between the kitchen and royal appartments copyright Angela Routledge, Wakefield Council

The project funded will be a geophysical survey of two parts of the castle, which during its history was the main royal castle in Northern England, not previously investigated. The survey will be of two areas of the castle using Magnetometry, Resistivity and Ground Penetrating Radar (GPR)

The focus is on parts of the castle not previously explored by  excavations in the 1980s, especially around the northern ramparts. This area stretches from the Swillington Tower towards the Kings Tower, and includes several earthwork features which remain unidentified, or unconfirmed.  Geophysical investigation is likely to reveal several interesting features including the link wall between the curtain wall and the Swillington Tower, which is unique in that it was built outside the main castle defences.

A second area that we have very little information on is part of the castle known as the “service buildings”. This area has never been excavated and we have very little knowledge regarding the layout or function of this part of the castle. 

As yet it is unclear when the survey will be undertaken.

Raby, Co Durham:

Aerial View of Raby Castle copyright Raby Castle

The Trust will be co-funding the project which aims to improve the understanding of the castle in the medieval period, especially around 1400 in the decades immediately after the licence to crenellate, with a buildings survey and development of a 3D model.

Once a stronghold of the Neville family, it moved into the ownership of the Vane family in 1626 and has been much altered and modernised, especially in the Victorian period, into a palatial family home.  Large sections of the medieval castle survive intact, albeit intersected and extended with more recent architectural additions.

This project seeks to strip back the more recent layers, to make sense of the medieval castle. Our aim is to create a 3D visualisation of Raby Castle in around AD 1400, helping us to visualise and to understand (where possible) how it functioned before the later additions.

In addition to boosting our understanding of the castle, the plan is also to train up a team of volunteers in how to carry out a building survey.

The aim is to start the survey work in April. 

Shrewsbury, Shropshire:

Shrewsbury Motte Top copyright Nigel Baker

This is the third project the Trust has funded on this important castle of the Welsh Marches and is an excavation of the motte top. The first two excavations in the inner bailey discovered that the original inner bailey was a lot smaller than it is today with little room for any substantial buildings, especially the royal hall.

This leaves only the motte and the aim is to understand the structural sequence and assess the character and the status of the buildings there: specifically to identify the royal hall known to be present during the Middle Ages.

The excavation is due to take place in the second half of July.

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Featured image Shrewsbury Castle by air courtesy of Shropshire Council