The fruits of Radovan Karadzic’s hate lay thick in the dense forest west of Srebrenica. Even one year after the July 1995 massacre of more than 7,500 Bosnian Muslims, the ground in the forest was littered with bones.

Some had been killed in ambushes as they attempted to flee the enclave. Their skeletons formed trails along the failed escape routes. Every now and then a single corpse would stand out among the rest. At one point, at a track junction among the trees, the body of a man in a pinstripe suit had been lashed with barbed wire to a concrete post. There were no bullet marks on the post. Knives had been used.

Among many of the local Serbs in those remote eastern Bosnian villages, a cult of the dead still lingered. It was not just the old who believed in vampires and ghosts and there was widespread credence that the spirit remained near the body for at least a year after death. So for the most part only a few woodsmen ventured into the hills where so many Muslims were killed the previous summer, and the forest remained silent, eerie and empty. I can’t remember any birdsong.

Yet if they were frightened of ghosts, the Serbs had little respect for the bodies. The drivers of the timber trucks that worked the forest lanes preferred to grind the corpses under their wheels rather than roll them away.

Most victims lay not among the trees but in mass graves, having been rounded up, executed in batches and bulldozed into the soil. Most had been driven by coach to the execution sites. Blindfolded, their hands tied together, they were mown down in lines by Serb death squads. The coach drivers – civilians – were then ordered to administer a coup de grâce with a pistol, ensuring their complicity and silence.

It was probably not a task they found distasteful. For Dr Karadzic’s greatest success in Bosnia, one that still outlives his failed war strategy, was his genesis of Serb loathing.

It knew no age barrier. I remember one wounded Bosnian soldier who did manage to escape from Srebrenica telling me that an elderly Serb man had discovered him lying in a hedgerow, exhausted, unarmed, and with gunshot wounds to his arm.

The pensioner beat him with a crowbar, then went away to fetch a knife with which to finish him off. The soldier crawled away and saw the man return, crowbar in one hand, knife in the other, beating the hedge line as if searching for a wounded animal.

There was no compassion or quarter given during those terrible July days of 1995. A handful of wounded men crawled out from the mass graves at night, but hardly anyone survived.

If the scale of Srebrenica was unusual, the genocidal passions behind it were by then familiar. From the start of the war Dr Karadzic had conjured a pathological hatred among the state’s Serbs for Bosnia’s majority Muslim population – Balija, as they were pejoratively known. He engendered his rabid brand of nationalism through a combination of fear and history. Harking back through Bosnia’s fratricidal experiences of the Second World War to the days of the Ottoman Empire, he offered the vision of a Greater Serbia as the only sanctuary against the contrived threat of a new Islamic State.

“Do unto them now as they shall surely do to you tomorrow,” was his call. Thus it was that 10,000 died in the Sarajevo siege; women and children were killed for sport by snipers; rape became a weapon of war; massacre was established as a necessary component of “ethnic cleansing” – the new euphemism for purge and pogrom; concentration camps reappeared on European soil; and killing begat killing until by the war’s conclusion more than 200,000 were dead.

If only the Srebrenica victims were my most salient memory of that hatred. They are not.

In the last days of the war I saw something in the yawning doorway of a derelict house outside Sanski Most, in western Bosnia, that 13 years later still zips through my mind untouched by time. The garden outside was an overgrown tangle of grass and a hot afternoon sun bleached the colour from the walls of the building, earlier burnt by advancing Serb troops. A sweet stench weighted the breeze. By then I had seen hundreds of bodies, most Muslim, most civilian, murdered out of combat by knife or bullet. Even so, I was unprepared for what waited in that house.

For a few moments after walking through the door I could not understand what I was looking at. The walls and ceiling appeared splattered in black, undefinable lumps, the floor was concealed by a gateau of twisted limbs and swollen torsos. It was as if an abstract charcoal sketch by Goya had come to life. Slowly, as my eyes became accustomed to the light, I could make out that there were 12 bodies. Then I saw their heads, or what was left of them. For these 12 men had been killed with a sledgehammer.

Before and since I have seen greater numbers of victims of execution. But the level of effort and involvement and hatred required to shepherd 12 men into a room, then smash in their heads with a hammer, left more of an impression than the horror of the mutilation itself and transcended the mere scale of murder.

Separated by time and geography from the scene of crime, Dr Karadzic looks an unlikely war criminal. Even the crimes with which he is charged sound clinical – until the memories come back, and “ethnic cleansing” and “genocide” stop being words but walls coated in skull fragments and brain.

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