It's called the pottery store rule: “you break it, you own it”. But it doesn’t just apply to pots and mugs, but to nations. In the build-up to the catastrophic invasion of Iraq, it was invoked by Colin Powell, then US secretary of state. “You are going to be the proud owner of 25 million people,” he reportedly told George W. Bush.

“You will own all their hopes, aspirations and problems.” But while many of these military interventions have left nations shattered, western governments have resembled the customer who walks away whistling, hoping no one has noticed the mess left behind. Our media have been all too complicit in allowing them to leave the scene.

Libya is a striking example. The UN-authorised air campaign in 2011 is often lauded as a shining example of successful foreign intervention. Sure, the initial mandate — which was simply to protect civilians — was exceeded by nations who had only recently been selling arms to Muammar Qadhafi, and the bombing evolved into regime-change despite Russia’s protests. But with a murderous thug ejected from power, who could object?

Today’s Libya is overrun by militias and faces a deteriorating human rights situation, mounting chaos that is infecting other countries, growing internal splits, and even the threat of civil war.

Only occasionally does this growing crisis creep into the headlines: like when an oil tanker is seized by rebellious militia; or when a British oil worker is shot dead while having a picnic; or when the country’s prime minister is kidnapped.

According to Amnesty International, the “mounting curbs on freedom of expression are threatening the rights Libyans sought to gain”. A repressive Qadhafi-era law has been amended to criminalise any insults to officials or the general national congress (the interim parliament).

One journalist, Amara al-Khattabi, was put on trial for alleging corruption among judges. Satellite television stations deemed critical of the authorities have been banned, one station has been attacked with rocket-propelled grenades, and journalists have been assassinated.

Some human rights abuses began in the tumultuous days that followed Qadhafi’s removal, and were ignored by the west. Ever since the fall of his dictatorship, there have been stories of black Libyans being treated en masse as Qadhafi loyalists and attacked.

Thousands have been arbitrarily detained without any pretence of due process; and judges, prosecutors, lawyers and witnesses have been attacked or even killed. Libya’s first post-Qadhafi prosecutor general, Abdulaziz al-Hassadi, was assassinated in the town of Derna last month.

But it is the militias that filled the post-Qadhafi vacuum who represent the greatest threat to Libyans’ human rights and security. “Libya has been sitting on the international community’s back burner as the country has slipped into near chaos,” warns Human Rights Watch.

In an attempt to integrate militias into the state machinery, the weak central government pays 160,000 members of these often violent gangs $1,000 a month and charges them with upholding authority.

When residents of Benghazi protested against militia rule in June last year, 32 people were killed in what became known as “Black Saturday”. In another protest in Tripoli last November, 46 died and 500 were injured.

Under militia rule, Libya is beginning to disintegrate. Last summer forces under the warlord Ibrahim Jadran took control of eastern oil terminals, demanding autonomy and resources for Cyrenaica, the long-neglected oil-rich east of the country.

Oil exports collapsed from about 1.5m barrels a day to fewer than 500,000, costing the country billions of dollars. Although Jadran’s forces initially only drew support from the Magharba people, other ethnic groups have now joined his struggle.

It is these forces which hijacked a oil tanker this month, prompting threats from Libya’s prime minister that it would be bombed until US forces captured it this weekend.

One of the great perversities of the so-called war on terror is that Islamist forces have flourished as a direct consequence of it. Libya is no exception, even though such movements often have little popular support.

The Muslim Brotherhood and other elements are better organised than many of their rivals, helping to remove the prime minister, push through legislation, and establish alliances with opportunistic militias.

Ominously, Libya’s chaos is spilling across the region. The country is awash with up to 15m rifles and other weapons, and a report by the UN panel of experts this month found that “Libya has become a primary source of illicit weapons”. These arms are fuelling chaos in 14 countries, including Somalia, the CAR, Nigeria and Niger.

In what has all the hallmarks of mission creep, a small number of US soldiers are being sent to Tripoli to begin training troops. But a stable future for Libya seems remote, however much the country’s strife is safely hidden away from the headlines.

It is dividing along every fracture line imaginable: whether it be ethnic, tribal, regional or political. Most Libyans have failed to even register for upcoming elections.

There is a real prospect of the country collapsing into civil war or even breaking up. Unless there are negotiated settlements to its multiple problems, Libya will surely continue its descent into mayhem, and the region could be dragged into the mire with it. No wonder western governments and journalists who hailed the success of this intervention are so silent.

But here are the consequences of their war, and they must take responsibility for it.

By arrangement with the Guardian