Frederick the Great of Prussia was a friend of Voltaire and enjoyed ribald evenings with the philosopher discussing the intricacies of life’s dos and don’ts. Before becoming king he was persuaded by Voltaire to become a pacifist.

But on ascending to the throne he became the most ferocious and successful of Europe’s warrior leaders. He said of himself that he was “doomed to make war just as an ox must plow, a nightingale sing and a dolphin swim in the sea.”

So far the twenty first century has been far more peaceful than the twentieth. No world war and none are there likely to be, even though the great powers might have the occasional confrontation. Some say we are overwhelmed by small wars, understandably so since the media, especially the fickle eye of television, picks up on every altercation.

As Francis Bacon wrote, there has never been, nor will there ever be, a shortage of “seditions and troubles”. But in fact this century there have been no interstate wars and civil wars are down in number, way below their Cold War total when the big powers stoked their fires.

Perhaps war is sometimes necessary and just. Most people will say that of the American civil war when President Abraham Lincoln led the northern states of the USA against the slave-holding South and of the Second World War when Hitler, the most evil man on earth, apart from Mao Zedong, killed millions and attempted to exterminate the Jews, homosexuals and gypsies.

But a closer look at history can raise a question mark there.

Yes, slavery would have continued without the north’s victory. But most slaves simply became serfs. The vote and other advances that Lincoln gave them were whittled away by southern legislatures and courts.

Not until Martin Luther King arrived on the scene was true freedom realised in the 1960s and the US, for the first time in its history, could claim to be a democracy. Lincoln didn’t do half as much for black people as President Lyndon B. Johnson.

As for the Second World War was it necessary?

Hitler never wanted to fight Britain or Poland. He wanted the Polish-occupied port of German-speaking Danzig. He also wanted a free route to East Prussia through the Polish “corridor”. It would have been politically cheaper for Britain if it had pushed Poland to make that concession than to go to war, which Britain decided to do after Hitler, frustrated over his modest demand not being met, invaded Poland. Before World War 2 there were times when Hitler thought Germany would fight the Soviet Union one day, but not Britain or Poland.

Most people abhor war but there has always been a minority who like it. In Europe in the nineteenth century it was regarded as a right of passage for upper class young men to go out and captain wars and to duel.

The well-regarded English poet Siegfried Sasoon described the opening days of the murderous Battle of the Somme as “great fun”. “The act of slowly walking forward, showing ourselves openly” resulted in “extraordinary exultation”.

The great American novelist Ernest Hemingway, who volunteered to fight in the Spanish Civil War, wrote that he revelled in the “dry-mouthed, fear-purging ecstasy”. On the eve of World War 1 Winston Churchill told his wife how much the gathering storm excited him. According to the Israeli academic Martin Van Creveld, in his seminal book “More On War”, “Many warriors of all ages have compared killing with having sex”.

There are always alternatives to war if we think ahead and are prepared in some cases to spend time, money and political capital on pre-emptive action as we are on war.

A good example is the way the US has helped North Korea. It has built half of a peaceful nuclear reactor. For a time North Korea was America’s biggest aid receiver in East Asia. In return North Korea was prepared to suspend its nuclear bomb research. Why has this not worked? It is because every time the Republicans in Congress have sabotaged the political deals that were meant to compliment the aid-giving.

Failure in diplomacy means the “hounds of hell are unleashed”. In the last century hundreds of millions died unnecessarily and if President Donald Trump misplays his hand with North Korea millions more may soon die.

Western countries throughout their long history have fought more wars and killed more people than the world’s other nations.

Most Enlightenment thinkers agreed with Jean-Jacques Rousseau that man’s basic nature is neither good nor bad. It is events that can turn good people into bad.

Vladimir Putin, Barack Obama, Bill Clinton and George W. Bush are not bad men but they unnecessarily have led their countries back into a hostile relationship.

They should read more history.