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Bombing in North Rhine-Westphalia during the Second World War
Wednesday, 31 December 2025 by Oliver Fontana – Managing Director
Bombing in North Rhine-Westphalia during the Second World War
Air raids shaped many places in what is now North Rhine-Westphalia. Historical accounts, damage maps and aerial photographs help reconstruct these events. For today's construction projects, the key question is what reliable evidence can be assigned to the specific area.
What historical destruction tells us about today's construction sites
Bombing may give grounds to suspect unexploded ordnance. However, the extent of destruction in a city tells us neither how many unexploded bombs remain on a particular property nor whether it is safe to give the all-clear. Local evidence and the actual state of investigation are what matter.
Contemporary documents, archive collections and historical maps provide different evidence of past events. For a present-day construction site, that information is mapped to the relevant area and assessed alongside other investigation records.
Historical evidence and today's construction sites
Historical sources from the five administrative districts
Different attacks left different traces
The Baufachliche Richtlinien Kampfmittelräumung distinguish between strategic and tactical air raids, aircraft strafing and other types of attack. Target areas included cities, industrial facilities, transport links and military installations. Historical research must also consider alternative targets and bombs dropped in error or in an emergency.
The name of a known target is therefore not enough to reconstruct events at a particular location. Attack chronologies, written reports, maps and aerial photographs need to be read together. The boundaries of today's five administrative districts define administrative areas, not areas with uniform ordnance contamination.
A developer needs to answer a different question from a local historian: which information helps assess the planned groundworks on this particular site? A detailed account of the air war can be a starting point. A decision about an individual work area also needs the evidence to be located on a map, the records to be assessed and the planned works to be considered. FONTANA-EOD can be contacted to clarify these project-specific questions.
Useful research therefore starts with two separate descriptions: what is known about the history of the site, and what is planned there today? The two descriptions need to relate to the same area. A historical street name alone is no more sufficient than a current address without details of the work area. An extension project should also identify any new ancillary areas and the planned depths of ground disturbance.
Arnsberg administrative district: Dortmund
Dortmund City Archive presents an urgent message card dated 8 October 1944. It reports a home destroyed in the attack on 6 October. Contemporary documents of this kind provide evidence of an event and its consequences. They do not replace an investigation of the property as it exists today. Archive example from Dortmund.
This suggests a straightforward question when preparing a project: does the recorded address actually refer to the area being investigated today? Check the location against traceable maps and record where the document came from. Historical damage and present-day property boundaries answer different questions. Any subsequent street renaming or changes to buildings should remain apparent in the location comparison.
Detmold administrative district: Bielefeld
Bielefeld City Archive explains the attack of 30 September 1944 using photographs and written records. Its account identifies the archive collections used. These source references help readers check statements and base further research on the original records. Archive account from Bielefeld.
When using such collections for a project, record the photograph's date, location and archive reference together. An image without these details is difficult to find again or check geographically. Using it in a project report also differs from publishing the photograph: a link to the archive identifies the source, whereas reproducing an image requires a separate check of the usage rights.
Düsseldorf administrative district: Duisburg
The City of Duisburg's historical geoportal brings together earlier city maps, aerial photographs, information about street names and other records. These collections can help locate historical information on a map. A historical city map does not constitute official clearance for earthworks. Access to sources from Duisburg.
Old and new maps are particularly useful in property research when a report uses outdated street names. Identify which location matches are established and which still require professional assessment. A similar-looking street layout or plot shape should not be the sole basis for assigning a location. Comparing maps provides an initial orientation; it does not replace an assessment of the ordnance question.
Cologne: the end of the war in 1944/45
The exhibition at Cologne's NS Documentation Centre describes the succession of day and night raids up to the heavy attack on 2 March 1945. For historical research, this sequence shows why a single image may not cover every event. Documentation from Cologne.
When examining an aerial photograph, its date is therefore just as important as the area shown. An image taken before a documented event cannot show its later consequences. Equally, a later image may not reveal every earlier trace. When making an enquiry, it helps to provide available images with their dates rather than a collection of isolated extracts without a clear timeline.
Münster: historical photographs
Münster City Museum illustrates the consequences of the attack of 10 October 1943 through contemporary photographs. These records connect dates with observed damage. For a construction site, the geographical connection and any further available evidence still need to be established separately. Münster exhibition retrospective.
A photograph of street damage may be informative yet provide too little detail to define the exact limits of an excavation. When gathering records, ask where the photograph was taken and which direction it shows. Its value lies in a historical observation that can be checked. The other records are then used to determine separately which areas of ground need to be investigated for the planned works.
Terms, sources and professional assessment
How the records complement one another
Attack records
Reports and chronologies help place events in time. Sources may present different perspectives or have gaps in their coverage. A city name in a list of attacks is therefore not a finding about a specific land parcel.
For the project file, keep an organised set of records with each document's title, date, source and associated map. If two records conflict, retain both until the discrepancy has been resolved. A shortened summary may omit the very qualification that matters for the location or date. Wherever possible, pass on the complete document and clearly distinguish any notes you have added.
A report of damage to a facility and a report about a neighbouring street may refer to different events. Their dates, locations and present-day property boundaries are compared as part of the professional assessment. A single, precisely defined impact area can only be established after the relevant analysis.
Sequences of aerial photographs
Images taken at different times may reveal traces later obscured by further attacks or changes to the site. Image scale, quality and geographical coverage affect what can be assessed.
A clear screenshot is not a complete professional aerial photograph assessment. To assess such work, the images used and their geographical coverage need to be documented in a traceable way. If a report already exists, ask for the accompanying plans and the findings it describes. Missing appendices should be identified before commissioning further work. The Historical aerial photograph analysis service page explains how the records and investigation question are brought together.
Current site plans
Historical evidence needs to be related to the area under investigation today. Changes to buildings and topography can make this difficult. Traceable reference points and clearly defined area boundaries are therefore important.
Provide a version of the plan that shows the planned groundworks themselves. For a utility project, for example, this means the route and work areas; for foundations, the planned points or areas. A property boundary can add context to the plan but does not automatically define the full scope of work. Access routes, temporary construction roads and other ancillary areas involving ground disturbance should also be included.
Also indicate where the location or depth has not yet been decided. A clearly identified open planning question is more useful for coordination than a seemingly precise drawing whose underlying assumptions later change.
Relating the city's history to the construction site
A documented attack is evidence of a historical event. A possible impact point identified in an aerial photograph is more specific evidence of suspected ordnance. Both differ from an item of ordnance that has actually been found and from the results of a completed investigation.
What an aerial photograph assessment can establish depends on the images used, their coverage and the visible traces. The BFR KMR describe case-specific assessments of areas and individual points on federal government properties. The applicable state procedures and local requirements are also considered for each construction project.
Further explanations of the terms and distinctions are provided in the ordnance glossary. For questions about survey methods, occupational safety and documentation, the ordnance investigation knowledge section brings together the technical foundations.
From a historical event to a location-specific suspicion
These terms describe different states of knowledge. A historical record initially provides evidence of what was reported. A professionally assessed suspicion of ordnance connects evidence to a particular area or point. A find, by contrast, is an item that has actually been discovered and whose further handling falls to the responsible specialists and authorities. These stages should be kept distinct in discussions and reports.
The distinction matters in planning. Archive research addresses past events and uses of a site. A technical investigation examines a different question at the site as it exists today. An existing investigation report, in turn, needs to be read for its geographical and technical scope. Only then can its relevance to the planned project be assessed.
Distinguishing survey work, clearance and documentation
When selecting a survey method, consider the type of object being sought, the ground conditions, likely interference and access. Metal structures or limited survey conditions may affect the findings. The question is therefore not which instrument is generally the most powerful, but which approach can address the specific investigation task under the conditions present.
The report should then make clear what was investigated and what limitations applied. A document title such as “clearance” alone does not explain that scope. Read the accompanying plans, depth information and restrictions as well. A survey report documents the investigation and its limits. Where clearance work has actually been carried out, the clearance record documents the areas worked on, the clearance objective and the results. The survey service page helps you prepare a suitable enquiry; documentation is covered in more detail under processes and evidence.
Planning investigations during construction
According to the DGUV, merely watching excavation beside an excavator is not a state-of-the-art ordnance survey. An investigation during construction must therefore be distinguished from general site supervision. Whether it is suitable for the remaining areas needs to be assessed against the specific suspicion and planned groundworks.
The BFR KMR describe a coordinated approach combining surveying with controlled progress of the works. Poor survey conditions do not automatically mean that any form of construction supervision will suffice. Identify the affected areas and limitations in the enquiry. The appropriate next step is to clarify the requirements for construction-phase ordnance surveying.
Coordinating historical assessment and technical investigation
The BFR KMR explain how air raids are assessed historically and how aerial photographs are analysed. Their assessment principles describe how an area assessment is developed; the Scope of application section relates to federal government properties. The local route to an assessment is described by the Arnsberg district government, the City of Cologne and the City of Düsseldorf. The North Rhine-Westphalia Ministry of the Interior describes the state service's role in public hazard prevention and response.
Ground conditions, target objects and interference determine the choice of method. The fundamentals of geophysical methods explain the physical principles. The planning requirements in the BFR KMR relate the works to the investigation objective; the Documentation section brings the scope of work and findings together. The DGUV questions and answers on ordnance clearance explain, among other things, why simply watching excavated material does not replace a technical investigation. The specification for construction-phase ordnance clearance describes how surveying is combined with controlled progress of the works.
Responsibilities, qualifications and occupational safety
Clarifying the site through the responsible local authority
In North Rhine-Westphalia, the state ordnance disposal service is based at the Arnsberg and Düsseldorf district governments. For Arnsberg, Detmold and Münster, KBD Westfalen-Lippe describes applications for wartime aerial photograph assessments being submitted by the local public order authorities.
Local contact arrangements can differ. In Düsseldorf, the fire service receives the relevant applications. Cologne describes forwarding them to KBD Düsseldorf and considering the assessment result alongside a case-specific statement from the public order authority. The actual local procedure should therefore be established for each project.
Private specialist companies carry out the professional services agreed for the project. The responsible state and local authorities perform their respective official duties. Information about this division of responsibilities is available under responsibilities of the authorities and specialist companies.
Matching responsibilities and qualifications to the task
Official procedures, the selection of a private contractor and occupational safety serve different purposes. § 7 of the German Explosives Act concerns the permit for the commercial activities involving explosive substances specified in that section. § 20 governs the certificate of competence for the responsible persons specified there. When commissioning work, consider the actual activity and the authorisation required for it. A general reference to the Act does not establish that the authorisation covers the task.
To protect employees, the employer determines the necessary safety measures under Section 5 of the Occupational Safety and Health Act through a risk assessment. The DGUV Information 201-027 covers risk assessment and protective measures in ordnance clearance. The First Ordinance to the German Explosives Act sets out, among other things, technical knowledge and training requirements for relevant activities. DGUV Rule 113-003 must be considered within its applicable scope. Occupational safety, the specialist service and the local authority's decision are assigned to the parties responsible for each.
What needs to be clarified for your project
Choosing the next step for your starting point
The next professional step depends on the information already available and the decision needed for the construction project. A historical location reference, an existing investigation report and an area with limited survey conditions each present a different task. Where several of these apply, their combined implications for the planned groundworks are assessed.
Historical information is available, but its connection to the site is unclear
You have a report about an air raid but cannot yet reliably relate it to the property. Prepare the complete report, its source details and a current site plan for the assessment. Mark the uncertain location reference and explain why you suspect a connection. This keeps the document's actual statements separate from a location match that still needs to be checked.
The aim is a traceable assessment of the information available. Choosing a particular survey method immediately would be premature in this situation. First establish what reliable information supports the next planning step and whether further records are needed.
An investigation report exists, but the construction project has changed
An earlier investigation may be relevant to the new project. What matters is whether its documented scope covers the works now planned. Compare the old report with the current plan. Mark any additional areas, relocated borehole positions or changes to the depth of ground disturbance. Include the report's appendices: a conclusion page alone often does not show the investigation boundaries clearly enough.
The professional assessment then asks which parts of the earlier findings remain applicable and where further clarification is needed. This does not imply either repeating every investigation automatically or accepting every earlier finding unchanged. The comparison identifies the actual decisions required.
The area is accessible but contains structures or sources of interference
Describe the existing surfaces, known utilities, foundations and other obstacles as precisely as possible. Photographs can show access conditions or the surface; utility and as-built plans add further information. These records help assess survey conditions but do not themselves provide investigation results.
Coordination should establish which areas the proposed method can investigate reliably. Areas not investigated or with limited interpretation must remain identifiable in the findings. A suitable alternative investigation or construction-phase approach is assessed for the particular groundworks. Simply describing an area as “difficult” is not a sufficient specification of the service.
Tendering is under way, but the investigation scope is still open
State the forthcoming decision and the version of the plan needed to make it. For a tender, for example, it may be important to establish which existing findings form the basis and which investigation still needs to be commissioned. Separate known information from assumptions. A bidder should be able to identify the records available and the area covered by the service.
Preliminary ground or environmental investigations may themselves disturb the ground. Their locations and depths therefore need to be included in the coordination. A later date for the main excavation does not put earlier drilling outside the assessment. Clarify the investigation requirements for these preliminary works before they begin, and record the agreed steps.
Keeping results understandable for later use
The BFR KMR emphasise clearly locating investigated areas and making the work and its results traceable. In a project file, this means keeping the report and its associated plans together. The version, date and description of the investigation scope should also be easy to find. A short email giving a result does not replace these records.
Such a filing system makes comparisons easier if plans later change. Record which report relates to which version of the plan and which questions remain open. Keep supplementary statements alongside the same records. The next person involved can then understand the basis for a decision without having to reconstruct the entire correspondence.
Records, the construction site and survey equipment
Frequently asked questions
Is every property in North Rhine-Westphalia contaminated by ordnance because of the air war?
No general claim of that kind can be made. Historical events may provide grounds for suspicion. For a particular area, what matters is the records that can be assigned to it, existing investigation results and the professional or official assessment.
Does a destroyed building prove that an unexploded bomb remains underground?
A record of building damage initially establishes the damage it describes. It does not, on its own, prove or rule out the presence of an unexploded bomb. Further local evidence is needed.
Why are aerial photographs from different dates assessed?
Later attacks or changes to a site may obscure earlier traces. Suitable images from several dates help assess the evidence in its historical sequence. The quality and coverage of the available material still need to be considered.
Do historical online maps provide clearance for earthworks?
No. They can help with historical orientation. An assessment for a construction project needs to relate to the area concerned and the relevant records and investigations.
Who should I contact about a specific construction-site question in North Rhine-Westphalia?
Clarify the local procedure with the responsible local authority. Prepare existing statements, a site plan and a description of the planned groundworks. In Cologne, for example, the KBD assessment result is considered together with the statement from the public order authority.
When should historical records be considered in planning?
As soon as the affected areas and planned groundworks can be described. This allows the reliable information already available and any gaps to be identified before an investigation or tender. If the location or depth later changes, the earlier assessment is checked to establish whether it still covers the project. Keep the investigation report, site plan, documented depths and limitations together for future use. Any clearance work carried out is additionally documented in the clearance record.
What determines the work involved in clarifying a project-specific question?
The extent and usability of existing records, the geographical question and the investigation steps still outstanding. For technical work, access, ground conditions and interference are further factors. A useful enquiry describes these conditions. A flat price based on a city name alone would not explain the actual work involved.
What should you do if a suspicious object is found?
Stop work in the affected area, do not touch or move the object, and keep your distance. In Germany, notify the police immediately on 110 and follow their instructions. Further identification and handling belong to the responsible specialists or authorities. A normal project enquiry does not replace reporting a find.
Records for your enquiry
Four questions for your planning
Which area is involved?
Mark the project on a current site plan. Do not assume that a historical location reference and today's construction-site address identify the same place without checking.
If the site has several separate areas, give each a clear name. Use the same names in the plan, enquiry and subsequent questions. This distinguishes, for example, an initially investigated excavation from an extension area planned for a later stage. A shared postal address should not obscure those differences.
What groundworks are planned?
Describe the planned geographical extent of works such as an excavation, utility trench or foundation. The word “construction” alone leaves important questions unanswered.
Include the relevant preliminary works as well as the main structure. What matters is the actual ground disturbance planned, rather than only the building's future use. If the maximum depth or the location of individual points is still being agreed, make the provisional nature of that information clear in your enquiry.
Which records are available?
Gather complete official correspondence, aerial photograph assessments and earlier investigation reports. Include maps, appendices and any stated limitations.
Do not select records solely because their findings seem favourable. Earlier differing conclusions or reports containing limitations may also matter for the assessment. A short list of filenames and plan versions helps with the handover. Include the original appendices where the text expressly refers to them.
What remains unclear?
Record missing information and differences between plan versions. The investigation required can only be established in relation to the actual starting conditions.
State the decision needed as precisely as possible: is the question about preparing an investigation, assessing an older report or checking it against a changed construction sequence? A precise question prevents different parties from interpreting the same enquiry as a request for different services. An overview is available in the section Quotation information and project documents.
Discuss historical records for your construction site
The exact location, planned groundworks and existing findings are central to a project enquiry. Gather the records and identify the open questions. Agree the official procedure with the responsible authority. For projects outside North Rhine-Westphalia, the contacts and procedures applicable to the project location are established separately.
If you would like an existing report assessed, provide it with its appendices and the current site plan. Explain what information you need for the next decision. FONTANA-EOD can discuss the project-specific investigation requirements with you.
Ordnance investigations for projects in North Rhine-Westphalia · Information for a project enquiry · More technical articles
Have your project assessed
Whether historical aerial photograph analysis, explosive ordnance surveying, surface surveying using GPR, magnetometry or TDEM, deep-ground surveys, downhole surveys, excavation supervision, area clearance or ordnance recovery is needed depends on the location, ground disturbance, depth, ground and existing documents. An early ordnance assessment provides clarity for tendering, programming, occupational safety and construction.
FONTANA-EOD combines its Section 7 SprengG licence, specialists holding Section 20 SprengG certificates of competence, suitable survey and clearance methods, and traceable documentation. Send the site plan, depth of ground disturbance, construction phase and existing documents for an initial technical assessment.
