British WW2 War Diaries: How to Find, Read and Convert Grid References

Every British military unit that served in Normandy was required to keep a War Diary, a daily record of where it was, what it did, and what happened to the men in it. For anyone tracing a relative's regiment, or trying to work out exactly where a particular action took place, these diaries are usually the single best primary source available.

They can also be hard going at first. The handwriting varies from officer to officer, the abbreviations take some getting used to, and almost every entry of any military significance ends with a grid reference in a system nobody uses any more. This guide covers where to find your unit's diary, how to read its grid references, how to convert them accurately, and how to match them against the actual wartime maps the diary was written against.

What's in a War Diary

A War Diary is a day-by-day log, usually kept by the adjutant or a nominated officer, covering a unit's actions, movements and events. Entries typically include the date and time, the location, a short account of what happened, and often the names of officers involved. Casualties, when they occurred, are usually recorded, along with appendices such as operation orders, patrol reports, and intelligence summaries.

Most original diaries are held at the National Archives in Kew, catalogued under the War Office (WO) series, most commonly WO 171 for units that served in North-West Europe from 1944.

Finding Your Unit's War Diary

Start with our own War Diaries section, where we've transcribed a growing number of British unit diaries ourselves, free to browse. It's grown a great deal since we started: what began as a handful of units is now hundreds of transcribed pages across dozens of regiments, brigades and specialist units, mostly covering the Normandy campaign from June to August 1944. If your unit is already there, it can save you everything else in this section.

If it isn't, the next stop is a community rather than an archive. Forums like ww2talk.com are staffed by experienced researchers who've spent years in this material, and plenty of diaries have already been photographed and shared in forum threads over the years, so it's worth searching for your unit before you go any further, then posting your unit and date range if nothing turns up. Some members run their own lookup services: one long-running thread has a member who checks whether a file exists at Kew and, for a fee to cover photographing and posting it, sends you a copy without you needing to order through the Archives or visit yourself. Terms and pricing on these community services shift over time, so check the latest replies on any thread before relying on a quoted price.

Failing that, go to the source. The National Archives' own catalogue, Discovery, lets you search by unit name. Regiments and corps changed names, amalgamated, and split over the decades, so it's worth trying a few variations, for example searching for "Green Howards" as well as the fuller "Yorkshire Regiment (Alexandra, Princess of Wales's Own)". It helps to know the WO reference before you go any further, since Discovery's search results can be broad and it's easy to end up with the wrong battalion or the wrong year.

Once you've found the right catalogue entry, you have two options. Visiting Kew in person means registering for a reader's ticket and reserving the documents in advance, but once you're there you're allowed to photograph the documents yourself, so bring a camera and create your own copies for later use. Alternatively, you can ask the National Archives to make a copy for you, but this can get prohibitively expensive: at the time of writing it's £9.92 for a page count, then £1.52 per page, and a single month of a war diary can run to 25 pages. Either way this is the slowest and most costly of the three routes, which is why it's worth exhausting the first two before committing to it.

Reading Grid References in a War Diary

Almost every entry that describes an action, a position, or a movement will include a grid reference, and this is where a lot of researchers get stuck. British units in North-West Europe used what's usually called the Modified British System, laid over one of two underlying projections depending on where the action took place. In Normandy that means French Lambert Zone 1, which extends to just west of Rouen, and Nord de Guerre, which reaches down to just west of Caen, so the two overlap across a band of the battlefield in between. Where both applied, the Normandy war diaries seem to have favoured French Lambert Zone 1, but the overlap is worth knowing about: if a converted reference lands somewhere that makes no sense, the entry may have been written against the other grid.

The basic idea is a series of nested squares. The area is first divided into large 500km squares, each given a single letter. Within each of those, 25 smaller 100km squares are lettered A to Z, skipping I to avoid confusion with the number 1. A full reference starts with two letters identifying which 100km square you're in, for example vT or rB.

In practice, though, the diary itself will rarely give you those two letters. The unit writing it already knew which 100km square it was operating in, so it usually didn't bother spelling it out, and you're left to work out the prefix yourself from context, typically the rest of the diary's narrative or the general area a formation is known to have been operating in that day.

After the letters comes a string of numbers giving the position within that square, an easting followed by a northing. War diaries most often used six-figure references, though you'll also come across four-figure references for a rough location and, occasionally, eight-figure ones for real precision. A typical reference might read something like 908812, or the diary might round it down to 9081, with the vT prefix left for you to establish rather than written on the page.

Converting Grid References with Our Coordinate Converter

Once you've got a grid reference out of a diary, the next step is turning it into something you can actually place on a modern map. That's what our WW2 Coordinate Converter is for.

Enter the numbers as written in the diary, and it will plot the location for you on a modern basemap. It supports both French Lambert Zone 1 and Nord de Guerre. For a Normandy diary, French Lambert Zone 1 is usually the one to try first, but if the result doesn't fit the diary's narrative and you're in the band where the two grids overlap, it's worth running the same reference through Nord de Guerre before assuming a mistake in the diary. Since the diary usually won't give you the two-letter prefix, the converter has a lookup tool built in too: it shows a Google Map with the grid squares overlaid, so you can match the prefix to whichever square fits the area you already know the unit was operating in from the rest of the entry.

Where we hold a georeferenced copy of the original wartime map for that area, the converter uses it directly, matching the grid printed on the actual sheet rather than a generic mathematical projection. That matters, because wartime cartography wasn't always perfectly consistent, and a formula-based conversion can drift by a meaningful distance on the ground. Where we don't yet have a georeferenced sheet for an area, the converter falls back to a projection-based conversion, still built specifically around the grid system the diaries use rather than a generic tool.

The Maps Behind the Diaries

Grid references only really come alive once you can see them on the map the diary's author was looking at. British forces in Normandy worked from two main map series, and it's worth knowing the difference.

GSGS 4250 was the 1:50,000 series, produced by the Ordnance Survey and used for divisional and corps-level planning, giving a wide view of an area with 10-metre contours, road and rail classification, and the grid system referenced throughout the diaries. Most grid references you'll come across in a war diary sit comfortably on a 4250 sheet. Our guide to the GSGS 4250 series covers how the series was made and what it shows.

GSGS 4347 was the companion 1:25,000 series, a much closer view used at battalion level and below for planning attacks and coordinating artillery, detailed enough to show individual field boundaries, sunken lanes and orchards, the kind of ground that decided whether a section could advance under cover. Our guide to the GSGS 4347 series has the full background, including the Defence and Going overprint variants you'll sometimes see referenced alongside diary entries about enemy positions or difficult terrain.

Both guides also include an index of known free-to-view scans of that series already available online elsewhere, so it's worth checking there before assuming a sheet you need hasn't surfaced anywhere yet.

We've been digitising original sheets from both series for some time now, and you can browse what's available so far in our map archive, sheet by sheet, alongside a modern basemap for comparison.

Putting It Together

In practice, researching a unit's movements tends to follow the same rhythm each time. Find the relevant entry in the diary, note down the grid reference as written, run it through the coordinate converter to see it plotted on a modern map, then pull up the matching sheet in the archive to see the same ground as the diary's author would have seen it. Done a few times over a diary's entries for a single day or action, it builds a surprisingly clear picture of a unit's movements, sometimes clearer than the prose of the diary itself.

Frequently Asked Questions

Where are British WW2 war diaries kept?

The originals are held at the National Archives in Kew, catalogued mostly under WO 171 for units that served in North-West Europe from 1944. You can search the catalogue on the National Archives' Discovery site, then either order a paid copy or register for a reader's ticket and view them in person, where you're allowed to photograph the documents yourself.

What grid system do British war diaries use?

Most use the Modified British System, sometimes called the "modified British grid", laid over French Lambert Zone 1 or Nord de Guerre depending on the area. In Normandy the two overlap, with French Lambert Zone 1 extending to just west of Rouen and Nord de Guerre reaching down to just west of Caen, and where both applied the Normandy war diaries generally favoured French Lambert Zone 1. A full reference has a two-letter prefix identifying a 100km square, followed by a string of numbers, usually six figures, giving an easting and northing within it, though diaries usually leave the prefix off and expect the reader to know or work out which square they're in.

How do I convert a grid reference from a war diary?

Enter it into our WW2 Coordinate Converter, which supports both French Lambert Zone 1 and Nord de Guerre, the two grids used across Normandy, and plots the reference on a modern map. The grids overlap across part of Normandy, and diaries there generally favoured French Lambert Zone 1, so try that first and Nord de Guerre second if the result looks wrong. If the diary hasn't given you the two-letter prefix, the converter's built-in lookup tool shows a Google Map with the grid overlaid so you can work out the right one from context. Where we hold a georeferenced copy of the original wartime sheet for that area, the converter uses it directly rather than a generic formula.

Which wartime maps did British units in Normandy actually use?

Mainly two series: GSGS 4250 at 1:50,000, for divisional and corps-level planning, and GSGS 4347 at 1:25,000, for battalion-level planning and fire coordination. Both are covered in detail in our GSGS 4250 and GSGS 4347 guides, and digitised sheets from both are browsable in our map archive.

Does Normandy War Guide have transcribed war diaries?

Yes. We've transcribed a growing collection of British unit diaries, free to browse at our War Diaries section, organised by unit and mostly covering June to August 1944.

Conclusion

A war diary on its own is a list of place names and numbers. Put it alongside a converted grid reference and the actual wartime map, and it turns into a day-by-day account you can follow on the ground. If you haven't found your unit yet, start with our War Diaries section, or head straight to the National Archives if it isn't there yet.

Phil – creator of Normandy War Guide
I started the site more than a decade ago after my first trip to Normandy and have been hooked ever since. I visit a few times each year to explore new sites and update the guide. Over the years I've also transcribed thousands of WWII war diaries and scanned original maps to keep this history accessible for everyone.