Interesting feedback to my recent blog posts about Fred Jane and his grading and classification system

I am extremely privileged to know Toby Ewin*, who has done very extensive research into the naval wargames being used by the Royal Navy and Imperial Russian Navy at the end of the nineteenth and beginning of the twentieth centuries. I was therefore very pleased when he wrote an extensive and very helpful critique of my blog posts which he has given me permission to quote from.

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Further to your latest blog, and its mention of Jane's view of the capabilities of different armour types around 1900, here is the Royal Navy's view at about the same time.

It is from the Naval Intelligence Department’s Report 617 of October 1901 (the TARGET BOOK ON RUSSIA, a copy of which is now in ADM 231/33 at the National Archives) which contains a helpful TABLE SHOWING EQUIVALENT THICKNESSES OF WROUGHT IRON, COMPOUND, ORDINARY STEEL AND SPECIAL ARMOUR.

In summary the table states ...

Simple rule of thumb. To bring into terms of Wrought Iron:

For Krupp face-hardened nickel Steel, multiply by 2.4.

For *KNC or Harveyed, multiply by 2.

Ordinary Steel or Compound, multiply by 1.7.

For 30 degrees with Normal add one-third the thickness.

(Other Target Books in ADM 231 files, about other navies, included the same data.)

In contrast, comparing the resistance of various types of armour plate to uncapped projectiles, the 1915 ADMIRALTY GUNNERY MANUAL gave the following values:

‘15in of wrought iron is the same as: 12in of compound, 12in of all-steel, 7½in of Harvey, 5¾in of Krupp.’

Expressing armour types in terms of the most modern Krupp armour — (is) surely better than converting them to inches of wrought iron, a type of armour that had been obsolete for a generation.

The strongest Great War side armour was of course on dreadnoughts, including the 350mm of Germany’s Kaiser, König and Bayern classes; 330mm of Britain’s Queen Elizabeth and R classes; 343mm of the US Nevada class, and 356mm of the Pennsylvania, New Mexico and Tennessee classes — culminating in the 406mm of the Maryland class laid down from 1919. The thickest pre-dreadnought side armour was the 457mm Harvey of the Black Sea Fleet’s Tri Sviatitelia, built 1891-96, which served through the Great War.

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This is extremely useful information, and I am very pleased that Toby has given me permission to share it with my regular blog readers, some of whom I know share my interest in naval wargaming.

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* Toby Ewin is Senior Visiting Research Fellow at the Laughton Naval History & Maritime Strategy Unit at King's College London. He read History at Cambridge before embarking on a career in the Civil Service. On his retirement he became a visiting scholar at St Andrews University before taking up his current position. One of his areas of special interest and research is naval history before and during the First World War, particularly the Black Sea conflict and Anglo-Russian naval relations.