The country is breaking up. Islamists are tightening their hold on its second-largest city and capturing the government's military stockpiles. The U.S. and the Europeans are evacuating their nationals and closing diplomatic outposts. We're not talking about Iraq. That's this week's news out of Libya.

This catastrophe—a word not to be used frivolously these days about the Middle East— has many fathers. Moammar Gadhafi, who was deposed three years ago this month, left Libya traumatized and without the semblance of a state. The militias that defeated him didn't put down their guns and soon started shooting at each other. Yet the U.S. and its NATO allies that helped topple Gadhafi also share responsibility.

The current conflict pits former Gadhafi loyalists against tribal or regional armies, the eastern areas around the second-largest city of Benghazi against the capital Tripoli, and Islamists against nearly everyone else. It is indeed complicated, but Washington and EU capitals exaggerate Libya's divisions to absolve themselves.

Most Libyans want a unitary state, and in the first free elections in 2012 they voted in moderates. Again this June they elected representatives from the country's secular blocks and reduced the number of Islamists. The new parliament convened this week for the first time albeit outside dangerous Tripoli.

Libya's main problem since Gadhafi's demise has been the absence of an organized security force loyal to the central government. The militias have run free, and violence in recent weeks has escalated. Meanwhile the Islamists, rejected at the ballot box, moved in to take land and resources by force.

The group that claimed control over Benghazi last week includes Ansar al-Shariah, the militia that on Sept. 11, 2012 besieged the U.S. mission and CIA station, killing Ambassador Chris Stevens and three other Americans. As the fighting spread to Tripoli, refugees fled into Tunisia, threatening the Arab world's one bright spot.

As Libya flirts with failed statehood, many on the right and left are fast to pin the blame on NATO's bombing and use it to argue against intervening now in Iraq. As if a future under the Gadhafis was bright and stable before the West stepped in. For a real-life experiment of what happens when the U.S. doesn't help topple an anti-American tyrant, look at Syria. Over 150,000 are dead, the moderate anti-Assad forces lack adequate arms, Bashar Assad holds power and the al Qaeda-inspired and Qatari-funded Islamic State in Iraq and al-Sham took half of Syria and neighboring Iraq. It has declared a new caliphate.

The original sin in Libya was President Obama's retreat after the fall of Tripoli. Washington failed to organize and train a Libyan military and security force. It refused to seek U.N. peacekeepers to disarm the militias and collect the loose weapons. Money and arms flowed in from Qatar and other places to Islamist militias that filled the governance vacuum. Warnings that Libya could unravel were ignored. (See our Dec. 28, 2011 "MIA on the Shores of Tripoli," and Dec. 13, 2012 "Leading From Behind Qatar.")

A month after the attack in Benghazi, the Libyan political leader Mahmoud Jibril laid some of the responsibility for the instability at the feet of the Obama Administration. "After the collapse of the regime, the immediate task of our friends was to help us rebuild the government before they withdrew from Libya," he said. "The moment the regime fell down, they felt that their mission has been accomplished. I think it was a premature decision."

America's options in Libya today are far harder than in the months after Gadhafi's demise. Security assistance for the beleaguered government in Tripoli might help. What would really help the unsettled world is if Washington would recognize the lessons of Libya. America's intervention wasn't what caused the nation's turmoil. It was the abdication that came afterwards.