Six Campaigns picks six of history’s defining battles. Some are well-known, some less so. How did you choose them?

Alternating well-known and lesser-known battles seemed to me a good way of illustrating my theme of policy (determined by the nature of society)>strategy>campaign>tactics. In other words, what goes into shaping a battle – an audit trail of decision making. My Hastings, for example, is a very “spare” account, and the thread is easy to follow because most people know the overall story, which helps the reader to follow the rather more complex (but essentially the same) thread with Towton. Hastings is, of course, the real start of modern British history, and I wanted to show that it was far more than just a battle on a hill in Sussex.

Towton, I admit, was a battle of my boyhood, the first I ever studied, on foot, in short trousers. And the way the battle turned on three masterly tactical decisions is fascinating.

Waterloo chose itself: you simply can’t ignore it. But it’s not always studied in its context as Wellington’s army’s culminating battle, and a vindication of national policy.

D-Day was an entire battle in itself, not just the beginning of a campaign. It was the end of a fascinating policy>strategy>campaign thread (as well as, of course, the essential springboard of the NW Europe campaign). By focusing on Sword Beach – the most important of the allied divisional landing sectors – I could get down into the tactical long grass and demonstrate just how the highest-level decisions, including those of Churchill himself, worked themselves out at battalion level and below.

Imjin River: in the same way, I’m drawn to how Truman’s decisions in the White House led to an infantry brigade group fighting the British Army’s largest defensive battle in the past 75 years. That, and how a demoralized allied army was turned round in short order by a brilliant commander who understood that nothing would go right on the ground unless clarity could be brought to the campaign plan.

And then I felt I must end with the British Army’s most bruising battle of recent years – Operation Panther’s Claw, in Helmand. In many ways it’s still too raw to probe, but I wanted to tease out that same policy>strategy>campaign>tactics thread.

With regard to your excellent account of the Hastings campaign of 1066, without getting into the realms of alternate history, if Harold had left the northern Earls to their fate and not gone north, could he have met William’s army as it landed and defeated it?

I don’t believe that anything’s inevitable when it comes to war, unless one of the belligerents, wilfully or otherwise, ignores the principles of war. It would be easy to say that Harald Hardrada’s army was the lesser threat and could have been dealt with later rather than sooner, but King Harold couldn’t rely on the northern earldoms. England was still a relatively new polity, and frangible. And when he went north, he believed that the Norman threat had passed with the onset of bad weather in the Channel. If he’d not been drawn north, he could have met the invasion in full strength and quickly, and the Normans, with the October storms against them, would have had no hiding place. The question is though, what was Harold’s mental state? Did he truly believe he had God on his side? We’ll never know, of course.

Who would you rate as History’s finest general?

Oh dear: can I just say instead “General Winter”, who defeated both Napoleon and Hitler’s best generals?

And England’s/Britain’s finest general?

I think if you take my theme of policy>strategy>campaign>tactics, Marlborough comes out on top of Wellington, of whom (using that old avoidance clause of confidential reports) one could say “not fully tested”; by which I mean Wellington wasn’t tested at the policy level in the way that Marlborough was. As for WW2, Slim was the most admirable, but Montgomery was tested the more fully. To say that Montgomery made mistakes is to say that he made war.

You are known as both a historian and as a novelist – how do you manage to keep both roles separate and avoid the line becoming blurred?

I’m gratified that the question implies that I do! I’m also a journalist, and that’s another challenge. Frankly, I’ve never really been conscious of the need to try. Historical fiction has to be grounded in solid history, and history – if it’s to be read – has to have style and pace. I think the two can be complimentary without compromising one another. But I do admit to having a mind that can compartmentalize, and that probably helps.

Which war or campaign in history do you most enjoy studying and writing about, and why?

I’ve always, so to speak, dipped in and out of the First World War, as most military historians will have done, and most soldiers too. The first piece I wrote for History Today, for example, in 1991, was on the transformation of the British cavalry in the decade before 1914. But after writing The Making of the British Army (2009) I began thinking about WW1 more systematically, in part no doubt because of the approaching centenary. And I conceived the idea of telling the story of, as it were, the making of the British Expeditionary Force – its people, its organization and equipment, its thinking; and the War Office’s thinking about the BEF; and the Cabinet’s thinking about war. And how we threw away our small professional army needlessly in the first few months. The result was Fight the Good Fight: Britain, the Army, and the Coming of the First World War (2013). And then, to answer the second-order question “what on earth were we doing throwing bad strategy after bad strategy?”, I wrote the sequel Too Important for the Generals (2016). And during the centenary, I was writing a monthly 2,000-word piece for The Times on the course of the war in that particular month, and in November 2018 these collected pieces were published as Fight to the Finish: The First World War, Month by Month. I happen to believe that in many ways the war has far more to tell senior officers today than does the Second World War. “Relevance” isn’t of course a necessity when studying history, but for me it adds a special dimension and interest.

If (heaven forfend) in a hundred years you are only remembered for one of your books, which one would you like it to be?

I could say, perhaps, “I haven’t yet written it”; but it would please me if my first book – Light Dragoons: The Making of a Regiment (1992) – were remembered, as it might mean that my late regiment hadn’t been amalgamated or disbanded.

In the writing of military history there are obvious advantages in having been a soldier (or a sailor or an airman). Academic historians have not been shot at, have not been responsible for the taking, and losing, of men’s lives, have not endured the privations and stresses of active service – but do you think there are any disadvantages to military service for an author?

I think the preamble in many ways answers the question. I wouldn’t trade my psc (“passed staff college”) for a PhD. The two aren’t remotely comparable (and by “psc” I mean that to include military experience generally). The work of academic historians is of the first importance in establishing the facts. Without facts, you’re sunk. Interpretation is where it gets tricky, and the best academic historians have the breadth and depth to help interpret. Military experience is, I believe, ultimately indispensable when it comes to judgement – military judgement that informs decision-making. Moral authority comes with that experience, the authority to judge. However, intellect has got to match experience. The only disadvantage to military experience that I see can see is when the two are wildly out of balance.

In studying history should we attempt to apply the moral standards of today to events in the past – an example is slavery, as old as civilisation, so if we are to dump Colston’s statue should we not also demolish the Parthenon?

I’m not against statue toppling per se. I’d have dynamited Hitler’s if there’d been one. I’d have helped put the ropes round Saddam’s. And there’s an obvious objection to a monument lauding the institution of slavery. But that’s not the same as one that incidentally may be perceived as condoning it, as in the case of Colston’s, which is a monument to his philanthropy (if somewhat narrowly defined). I wish we could be a little subtler, by, say, erecting a statue of Lord Chief Justice Mansfield next to Colston’s, celebrating the 250th anniversary in June this year of his famous ruling, which did much to make way for abolition.

If time travel existed, with the exception of the obvious ones, such as the resurrection, which event in history would you most like to witness, with the aim of improving your understanding of its impact?

Oh, what a list! But high on it would be the “war council” in No 10 on 5 August 1914. As I write in Fight the Good Fight: “And so the war council – which Wilson [DMO] in his diary called ‘an historic meeting of men, mostly entirely ignorant of their subject’ – resolved to send the BEF to France, in a strength to be decided, to a place to be determined, and to operate along lines as yet unspecified. That it could have happened thus, after all the years of careful preparation, remains a cautionary tale for military planners and policy-makers alike.”

As a historian, who are the scholars and authors who have influenced you most?

Again, the list isn’t complete, but for intellect and wisdom, Sir John Keegan and Sir Michael Howard; for asperity, Sir Basil Liddell Hart; and for soldierly humanity, Field Marshal Lord Slim.

Allan Mallinson’s debut novel was the bestselling A Close Run Thing, the first in an acclaimed series chronicling the life of a fictitious cavalry officer before and after Waterloo. He is the author of 1914: Fight the Good Fight and his latest book is The Shape of Battle: A Study of Six Campaigns, from Hastings to Helmand.

Gordon Corrigan is a historian and the author of Mud, Blood and Poppycock.