A few days ago I was once again reminded of that as I prepared to cross into what is now known as the Democratic Republic of Congo (DRC) from neighbouring Rwanda.
Scattered across a hillside were hundreds of men dressed in fluorescent orange and pink overalls labouring on what appeared to be a giant building site.
"Convicts," said my Congolese driver by way of explanation after noticing my surprise at seeing the men. "They're Rwandan Hutus, men convicted of carrying out massacres during the 1994 genocide against the Tutsis," he elaborated.
By any standards it was an eerie encounter to have in Rwanda, but made even more so given it occurred just a few miles from the Congolese town of Goma that lay just on the other side of the border.
Back in the dark days of the Rwandan genocide, Goma made global headlines. As the massacre of Tutsis began, the town at first became a cross-border refuge for civilians fleeing the mass killing perpetrated by their Hutu tribal rivals.
Later, though, as the Tutsis regained power in Rwanda, Goma became an out-of-reach bolthole to which killer Hutu militiamen escaped to flee punishment for the war crimes and human rights abuses they had committed.
To this present day, Goma still reels from the after-effects of those tumultuous times and the role that was thrust upon it. Almost constantly since, it has been a volatile and dangerous place, and right now is no exception.
It was 2008 when I was last here. Back then, Goma found itself all but surrounded by rebel fighters led by a Tutsi commander called Laurent Nkunda. I interviewed him at his base in the bush.
Today, it is the turn of another Tutsi warlord, General Bosco Ntaganda – aka The Terminator – to lead the threat against Goma with a rebel force known as M23, shorthand for the March 23 Movement.
Like Nkunda in the past, General Ntaganda and his fighters consist mainly of Congolese Tutsis who defected from the country's army, and according to a recently leaked and controversial UN report, are backed by their Tutsi brethren within the Rwandan government of President Paul Kagame.
There is perhaps an element of historical payback involved in the current crisis. More likely though, the best explanation for what is happening today is that Mr Kagame and his men have one eye firmly fixed on annexing eastern parts of Congo in the hope of acquiring some of its vast and long fought-over mineral wealth and natural resources.
It's an allegation Kagame has worked hard at to refute, but few dispute.
What remains utterly indisputable is that here in eastern Congo there are territories in which the mineral coltan is to be found in greater abundance than anywhere else in the world.
In our modern gadget-filled age there is not a personal computer or mobile phone that works without this crucial ingredient after it is industrially processed into a compound known as tantalum and made into an electronic chip.
Across Congo, there are other valuable commodities to be found, including some of the best- quality gold on the planet.
During the last few years, I have witnessed in places like Mongbwalu in Orientale Province how both the legal and illegal mining of gold helps to fuel Congo's warlords and fighters, as well as line the pockets of those companies in the global commercial market.
According to a report published last week, gold is now the primary source of income for armed groups in eastern Congo and is ending up in jewellery stores across the world.
"Gold is very portable, you can put it in your pocket and it is easily smuggled across the border. You don't need a large quantity to make a lot of money," says an anti-fraud agent of the border custom in Goma.
According to the Enough Project, a human rights group that specialises in conflict minerals in Congo and Sudan, roughly $30,000 (£18,500) worth of gold can fit in a pocket and around $700,000 in a briefcase. While only 23kg of gold were officially exported from eastern Congo in the first half of 2012, something like two to four tons went out through illegal routes, according to the group's report.
General Ntaganda used to run an illegal mineral trade network when he was in the Congolese army, making millions of dollars each year from mines including Rubaya in Masisi.
Hardly surprising perhaps, that his men right now are trying to gain control of the same mine as part of their current offensive.
What this means for the ordinary Congolese in Goma, Masisi and other areas is that their lives are once again plagued by killing, rape and other human rights abuses as rival militias fight for control of territory and mineral resources on behalf of themselves and their benefactors.
Since April, almost one-quarter-of-a-million people have been displaced by violence linked to M23 and other militia groups.
Over the last few weeks, armed attacks and killings have terrorised Goma, and after dusk this once-bustling city becomes a ghost town as people cower indoors afraid of what might become of them on the streets.
In those months since the M23 threat to the city emerged, thousands of reinforcements from the Congolese army have been deployed. These soldiers, who are supposed to protect the city against a potential attack from the M23, have instead become the most concrete threat to the residents of Goma.
Over the past few days the rumour mill here has been rife with talk of a government offensive against the rebels.
However, civilians remain unconvinced that should an offensive occur it will make much difference to their safety and quality of life. Most likely, it will only exacerbate an already volatile situation.
For now, guns and gold remain the most dangerous collateral here. Such things are nothing new across this region.
As I wrote earlier, history has a nasty habit of repeating itself in Congo.