Don't look now, but another nation in the Middle East is falling to pieces.

This time it's Yemen, which was already the poorest nation in the region when a civil war broke out early this year. Things have only gotten worse since Saudi Arabia intervened with major military force.

It's a humanitarian disaster. But it also illustrates the increasingly obvious downsides to America's close relationship with Saudi Arabia. By not pushing the Saudis to back off, or even speaking out on their mistake, America is setting the stage for future disasters.

So what has happened? Ansar Allah, a Shiite group whose members are known as the Houthis, has been fighting an on-again, off-again insurgency against the Yemeni government since 2004. When the Arab Spring broke out in 2011, mass protests led to the resignation of Ali Abdullah Saleh, a Shiite who had been Yemen's president since 1990. Abd Rabbuh Mansur Hadi, Saleh's vice president, was elected on a single-candidate ballot as an interim president (the Houthis boycotted the election).

The chaos and general government weakness enabled greater Houthi boldness. In September 2014 they seized Sana'a, the Yemeni capital city, in protest over a fuel price hike. After a U.N.-brokered peace deal fell apart in early 2015, the Houthis retook Sana'a and proclaimed a new government, causing President Hadi to resign. He later fled the country, rescinded his resignation, and declared Aden (a port city in the south) the new Yemeni capital. As yet, the Houthis have not been able to take Aden.

That prompted the Saudis, with U.S. assistance, to begin attacking Houthi forces. Meanwhile, Saleh, obviously angling for a return to power, has ironically thrown his lot in with the Houthis.

The average Yemeni is naturally suffering horribly. How bad has it gotten? Here's Matt Purple:

The Saudis have been blockading Yemen since March to repel ships seeking to arm the Houthis. They've pledged $274 million in aid for the country they're bombing, but have demanded that Houthi-controlled areas be excluded and tossed up bureaucratic roadblocks that have made the effective distribution of supplies impossible. The result is that Yemen has been isolated from the world and left to die. More than 80 percent of its population — 21.1 million people — is in need of aid. Thirteen million are at risk from starvation and 9.4 million are imperiled by thirst. [National Interest]

The Saudis insist that this is all part of a regional Sunni-Shiite rivalry, a response to Shiite-dominated Iran's longstanding support for the Houthis. While that may have been true in the past, Iran reportedly urged the Houthis not to make a bid for power, worrying it would be a distraction from Iran's nuclear negotiations with the U.S. and other world powers. At any rate, whatever support Iran has given the Houthis is nothing compared to the current Saudi intervention.

In many ways this mirrors the situation in Iraq. Yemen has been chronically unstable for years, beset by corrupt government, repeated armed uprisings, and the poisonous legacy of Western colonialism. Yet foreign intervention, supposedly to help "stabilize" the country, is doing little but dragging out the conflict while causing mass suffering and death.

Perhaps the most jarring result of the Saudi intervention is that it has been a major boon to the local branch of al Qaeda. It has been able to operate openly in eastern Yemen, and seized control of Yemen's fifth-largest city in April, freeing hundreds of prisoners and stealing millions in cash. Though the U.S. military has continued to conduct drone strikes against the branch, apparently killing several al Qaeda members a few days ago, it's obviously not enough to counteract the freedom allowed by total political chaos.

And that in turn raises the question: Just what benefit is the U.S. getting from its support of the Saudi regime? Back in the days when huge gobs of Saudi cash were fueling bin Laden's rise to power, the answer was obvious: oil. However, since the fracking revolution, U.S. imports of Saudi oil have declined by 50 percent. But we're still effectively allowing them to smash a Muslim nation, starve its population, and create a haven for al Qaeda in the process. Why?

Editor's note: This originally article misstated Ali Abdullah Saleh's religious beliefs. It has since been corrected. We regret the error.