Professor Sir Michael Howard, who has just died at 97, was the greatest practitioner of military history, an inspiring teacher and academic innovator, and a disarmingly funny, warm and observant friend – almost to the last.

He took military history out of a cul de sac and made it part of general historical and humanities studies in half a dozen countries. His approach was based on direct, and brutal experience. He won a Military Cross leading his first platoon into action after the landings at Salerno in Italy in the autumn of 1943.

He had an outstanding gift for language – penetrating, elegant and brief. On one occasion I heard him sum up the Second World  War – “five regional wars wrapped in two global conflicts” – in 50 minutes. A few years later I heard him pull the same trick, in 2014, on the origins of the First World War. He covered the subject in 45 minutes. There was nothing banal or second hand, and not a word or pause out of place.

It was all helped by a private and public persona that was a touch theatrical, a delivery with a faint hint of the clipped tones of Noel Coward.

He educated the great, not least Margaret Thatcher, about soldiers and the military. He also taught the military about education for the contemporary world. He could change his views, on nuclear disarmament for instance, and embrace the new – foreseeing years ago the influence of climate change, migration, cyber and genetics on present and future conflict.

He was born into a comfortably well-off middle class family in Dorset, his father from Quaker stock and his mother from a wealthy German Jewish family – which had a profound influence on his view of Britain, Europe and the world.

After being educated at private school, Wellington, in Berkshire, he took a truncated history degree before signing up for service with the Coldstream Guards. After training in North Africa, his battalion was among the first across the beach at Salerno in 1943. His first action was leading his platoon against well entrenched machine gun positions in the hills above a few days later.

“I imagined I was a hero in some Western movie,” he later told me. “I suppose it was luck – get your gallantry award first and then you can get away with some horrible mistakes – I sometimes thought I deserved a court martial.”

The action led to the Military Cross. Italy that winter and the following one was a grind – one in which Michael was wounded and came down with malaria, which affected him for years.

One incident haunted him, too, for the rest of his life. When his patrol was blown up in the mountains above Bologna, he abandoned a wounded Guardsman, Terry, who later died. In his autobiography he frankly blames himself – though had he stayed, it probably would have meant the destruction of the whole patrol team.

This is recorded with astonishing frankness in his slim autobiography, “Captain Professor.” The Italian campaign had its touches of camp, too. A fellow officer was “Dickie” Buckle, later the famed balletomane and critic for the New York Times. Returning from a failed fighting reconnaissance patrol, Buckle was asked what was achieved. Buckle reported very little positive – two Guardsmen hit, and terrible weather – “but the violets were divine.” In Florence, Michael recorded driving round in taxis, holding hands with the precocious teenage Franco Zeffirelli, a self-appointed liaison officer.

The war left an enduring reflection: “We could never work out why the Germans were so bloody good.” The experience also left him with an enduring regard for the Guards, which was reciprocated. Asked one day for his favourite general of the war, he replied “Bill Slim – outstanding because his men simply loved him.”

After the war came a return to Oxford , and a “lousy degree – I was enjoying myself too much,” and the pursuit of academe – but with a difference.

His first jobs were at King’s College London, where he came to found the Department of War Studies. He would return to Oxford, first in War Studies, and then the Regius Professor of History. One of the main endeavours was to help politicians and public understand the disciplines of thinking strategy, policy and diplomacy. To this end, with Alastair Buchan, he founded the International Institute for Strategic Studies.

In parallel was the astonishing production of books, which have his unique brand of clarity and succinctness. He translated Clausewitz’s On War with his American colleague Peter Paret, and it is still the standard English version today. His study of the Franco-Prussian War was based on original research and focused on the social impact of the war in both Germany and France.

He also contributed to official histories on strategy and the Mediterranean theatre in the Second World War. A commission to write the official history of Intelligence in the war led to a close encounter with the vetting authorities, when he revealed that he was gay – which he had done little to conceal from friends. Nonetheless, the men in suits got their oar in by forbidding publication on security grounds – it didn’t appear till the end of the nineties.

Among the best, most original and accessible of his works, are the essays – which are the length of a Maupassant novella. Try his Clausewitz, A Very Short Introduction or his War and the Liberal Conscience. His Continental Commitment based on the Ford lectures raises Britain’s dilemma as a European or global actor, a problem which haunts the Brexit debate. One of his last books, The Invention of Peace, based on lectures in his last post as professor at Yale, explains that peace only became a concept in modern diplomacy with Kant’s influence in the Enlightenment.

His essay, The First World War, is a bravura tour d’ horizon without a footnote, adjective or comma out of place. I give it, along with Orwell’s Why I Write, to anyone aspiring to write history or current affairs journalism.

This is only part of the story. Michael was one of the most intriguing and subversively witty of companions and conversationalists. I only got to know him later in his life. He treated me like an errant research student – generally hailing me with “been anywhere really dangerous lately?”

We used to have extended lunches in which we swapped thoughts about recent books and articles. His whole approach was that history and journalism were complementary and must always be awake to new developments and nuances. He was devastating about the activities of George W Bush and the hubris of Tony Blair – and hated the whole notion of the “War on Terror”. Going to war in Afghanistan and Iraq, he described as “like fighting cancer with a blow torch.”

In the middle of it all was mischief and music. He had played oboe at school and loved classical opera. One lunchtime we agreed not to talk military, or history – but music. He then explained why he felt that the spiralling septet in the middle of The Marriage of Figaro was for him one of the most thrilling moments of musical invention and entertainment.

Fun was always there – I remember one conversation with his lifelong companion Mark James. Visiting him one summer afternoon, he declared, “there’s something really troubling me.” I feared an ominous prophecy coming on, some terrible undiscovered notion of apocalyptic warfare. “Perhaps you can help,” he said with a grin. “With all that security and personal bodyguards, how does a minor royal get a moment of intimacy? With all those people around it must be very difficult.” This is a slightly censored version of the quote – because I vividly recall the word “fuck” being in the question.

He looked on his pupils and friends for enlightenment. Last year he said, “when you visit next, tell me your latest thoughts on migration and what it means for us all. After all, you have been looking at this for a very long time.”

He also had a tremendous touch with bores. The standard approach when the bores were in incontinent flow was, “jolly good company. Must go. I have a train to catch.”

The last time he had to catch a train was last Saturday 30th November – with impeccable timing, the day after his 97th birthday.