Fifty years ago, EP Thompson's The Making of the English Working Class rescued the study of history from the powerful. Kings and queens, landowners, industrialists and imperialists had owned much of public memory.

In 1980 Howard Zinn's A People's History of the United States also demonstrated that the freedoms and rights we enjoy precariously - free expression, free association, the jury system, rights of minorities - were the achievements of ordinary people, not the gift of elites.

Historians, like journalists, play their most honourable role when they myth-bust.

Eduardo Galeano's Open Veins of Latin America (1971) achieved this for the people of a continent whose historical memory was colonised and mutated by the dominance of the United States.

The "good" world war of 1939-45 provides a bottomless ethical bath in which the West's "peacetime" conquests are cleansed.

Demystifying historical investigation stands in the way. Richard Overy's 1939: Countdown to War (2009) is a devastating explanation of why that cataclysm was not inevitable.

We need such smokescreen-clearing now more than ever.

The powerful would like us to believe that the likes of Thompson, Zinn and Galeano are no longer necessary - that we live, as Time magazine put it, "in an eternal present" in which reflection is limited to Facebook and historical narrative is the preserve of Hollywood.

This is a confidence trick. In Nineteen Eighty-Four George Orwell wrote: "Who controls the past controls the future: who controls the present controls the past."

The people of Korea understand this well.

The slaughter on their peninsula following the second world war is known as "the forgotten war," whose significance for all humanity has long been suppressed in military histories of cold war good versus evil.

I have just read The Korean War: a History by Bruce Cumings (2010), professor of history at the University of Chicago.

I first saw Cumings interviewed in Regis Tremblay's extraordinary film The Ghosts of Jeju, which documents the 1948 uprising on the southern Korean island of Jeju and the campaign by the present-day islanders to stop the building of a base with US missiles aimed provocatively at China.

Like most Koreans, the farmers and fishing families protested at the senseless division of their nation between north and south in 1945 - a line drawn along the 38th parallel by a US official, Dean Rusk, who had "consulted a map around midnight on the day after we obliterated Nagasaki with an atomic bomb," as Cumings writes.

The myth of a "good" Korea (the South) and a "bad" Korea (the North) was invented.

In fact, Korea, north and south, has a remarkable people's history of resistance to feudalism and foreign occupation, notably Japan's in the 20th century.

When the US defeated Japan in 1945 it occupied Korea and often branded those who had resisted the Japanese as "commies."

On Jeju, as many as 60,000 people were massacred by militias supported, directed and in some cases commanded by US officers.

This and other unreported atrocities were a "forgotten" prelude to the Korean war (1950-53), in which more people were killed than Japanese died during all of the second world war.

Cumings gives an astonishing tally of the degree of destruction of the cities of the North - Pyongyang 75 per cent, Sariwon 95 per cent, Sinanju 100 per cent.

Great dams in the North were bombed in order to unleash internal tsunamis. "Anti-personnel" weapons, such as napalm, were tested on civilians.

Cumings's superb investigation helps us understand why today's North Korea seems so strange, an anachronism sustained by an enduring mentality of siege.

"The unhindered machinery of incendiary bombing was visited on the North for three years," he writes, "yielding a wasteland and a surviving mole people who had learned to love the shelter of caves, mountains, tunnels and redoubts, a subterranean world that became the basis for reconstructing a country and a memento for building a fierce hatred through the ranks of the population.

"Their truth is not cold, antiquarian, ineffectual knowledge."

Cumings quotes Virginia Woolf to describe how the trauma of this kind of war "confers memory."

The guerrilla leader Kim Il Sung had begun fighting the Japanese militarists in 1932.

Every characteristic attached to the regime he founded - "communist, rogue state, evil enemy" - derives from a ruthless, brutal, heroic resistance, first to Japan, then the United States, which threatened to nuke the rubble its bombers had left.

Cumings exposes as propaganda the notion that Kim Il Sung, leader of the "bad" Korea, was a stooge of Moscow.

In contrast, the regime that Washington invented in the South, the "good" Korea, was run largely by those who had collaborated with Japan and the United States.

The Korean war has an unrecognised distinction.

It was in the smouldering ruins of the peninsula that the US turned itself into what Cumings calls "an archipelago of empire."

When the Soviet Union collapsed in the 1990s, it was as if the whole planet was declared pro-US - or else.

But there is China now.

The base being built on Jeju Island will face the Chinese metropolis of Shanghai, less than 300 miles away, and the industrial heartland of the only country whose economic power is likely to surpass that of the US.

"China," says President Obama in a leaked briefing paper, "is our fast-emerging strategic threat."

By 2020, almost two-thirds of all US naval forces in the world will be transferred to the Asia-Pacific region. In an arc extending from Australia to Japan and beyond, China will be ringed by US missiles and nuclear-weapons-armed aircraft.

Will this threat to all of us be "forgotten" too?

This article appeared in the New Statesman