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 He later fled the country, rescinded his resignation, and declared Aden (a port city in the south) the new Yemeni capital.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.

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 Week - By Ryan Cooper