Cuba. Vietnam. Hiroshima. Is Barack Obama trying to tell us something? I think yes. In the last months of American history’s most unexpected presidency, he is trying to bury, as quietly as he can, the dilemmas and memories that have haunted his generation of Americans: nuclear bombs that obliterated Hiroshima and Nagasaki in 1945, and the assault on Cuba and Vietnam in the 1960s.

As President he cannot apologise, for this would be toxic to those who fought, with courage and conviction, imperial Japan in the Second World War; and those who believed, with good reason, that they had saved the free world from Communism by their vigorous challenge to the Soviet Union. But to those who grew up in the 1960s and 1970s, Cuba was a folly and Vietnam a deadly mistake.

It is not entirely coincidental that Barack Obama was born in 1961, the year in which John Kennedy authorised the failed American invasion across the Bay of Pigs; and, a few months later, Washington and Moscow nearly blew up the world with a nuclear confrontation over missiles in Cuba.

President Obama knows that even regret can induce some bit of backlash; but he is also certain that he must pay this price. It may not be enough to fully exorcise such ghosts, but they must be laid to rest. We cannot erase tragedies of the past or deny their consequences, but there is substantial merit in public acknowledgement of a grievous error.

One decision by Obama in America-Vietnam relations is a game changer: America will sell weapons to Vietnam

Compared to the unprecedented bloodbaths we have seen in the last century, the wars, racism and genocide, the incident of 1914 in which Canada turned back hundreds of Sikhs on board the ship Komagata Maru, hardly ranks among the worst atrocities within memory. But it did leave deep scars on Sikhs, which continued to rankle. Canada’s young Prime Minister Justin Trudeau recognised the need for healing. His statement was carefully worded: “Canada does not bear alone the responsibility for every tragic mistake that occurred with the Komagata Maru and its passengers, but Canada’s government was without question responsible for the laws that prevented these passengers from immigrating peacefully and securely, for that, and for every regrettable consequence that followed, we are sorry.” The important point is the regret, publicly expressed. The very fact that it took a hundred years to come indicates how difficult it is for establishments to recognise, or at least admit, any injustice.

It took 71 years for an American President to visit the Hiroshima Peace Memorial. We should try and understand the complexity of the reason, rather than leap on to some “moral” podium and proclaim outrage. By 1945, America and Japan had been engaged in an epic war for three years, in which no quarter was asked and none given. The American leadership had to consider the human cost of invading imperial Japan, given the latter’s fearsome kamikaze reputation. And yet the sheer horror of nuclear bombs over Hiroshima and Nagasaki is inescapable. For me, the amazing truth is not that reconciliation is complete now, but that it began in the early 1950s. We must salute the generation, on both sides, that recognised, so quickly, that peace was infinitely preferable to havoc. The world is, consequently, a much better place.

When does another chapter of history begin? Always difficult to say, except when victory or defeat changes everything radically. More often, continuity is too blurred for sharp clarity. America did not open the door to Cuba on the day that Obama landed in Havana to a warm, if occasionally awkward, reception. That door was being nudged for years, which is the way that the diplomatic process works. Doors open by imperceptible inches, not in a dramatic flourish. What Obama’s visit ensured was that the gate would not be shut again.

But one decision taken by Obama in the equally slow manoeuvres of America-Vietnam relations is a game changer: America will sell weapons to Vietnam. The Vietnam war may have ended decades ago, but the last trace of enmity, which is suspicion, is finally over. This at long last is a reversal to the 1940s when the Communist legend Ho Chi Minh allied with America against Japan, confident that republican America would force Europe’s imperialists to decolonize once the war ended. [Gandhi supported the British in the First World War for similar reasons.] But Roosevelt died and his successor Harry Truman chose France over Vietnam. The rest is familiar.