When it comes to humanitarian rescues for persecuted minorities in northern Iraq, the U.S. military has valuable experience that may offer some lessons for the latest mission.

President Obama's call to help some 40,000 members of the Yazidi community, who are trapped on barren mountains and surrounded by the extremist Islamic State, has echoes of a 1991 U.S. effort known as Operation Provide Comfort.

In that episode, the U.S. military had just driven Saddam Hussein's Iraqi forces out of Kuwait, leaving his army in disarray. This prompted the Kurds in northern Iraq and the Shiites in the southern part of the country to rise up with the aim of toppling Saddam.

But Saddam and his army regrouped, retaliating in a ferocious campaign that featured helicopter gunships against the lightly armed rebels. The uprising was quickly quashed, but not before a half-million Kurds had fled their homes, seeking safety in the rugged mountains along Iraq's northern border with Turkey.

The U.S., which had encouraged the uprising against Saddam but did not provide military help, felt compelled to deliver humanitarian relief. President George H.W. Bush, working with Britain and other allies, launched Operation Provide Comfort. Thousands of U.S. air and ground forces delivered relief supplies and also protected the Kurds from the Iraqi army.

The humanitarian effort carried on for months before the region began to calm down and the Kurds started returning home.

President Bush described the operation as an "interim measure." He added:

"Our long-term objective remains the same for Iraqi Kurds, and indeed, for all Iraqi refugees, wherever they are, to return home and to live in peace, free from oppression, free to live their lives."

But the impact of that operation is still visible as the U.S. military returns to the same region to help the Yazidis, a small, ancient religious sect who are themselves ethnic Kurd.

So what lessons might be gleaned from that 1991 effort?

There are many. Here are two perhaps contradictory ones:

-- The humanitarian mission led to a no-fly zone over northern Iraq (and southern Iraq as well). U.S. warplanes patrolled the skies to keep out Saddam's army. That, in turn, led to the establishment of the semi-autonomous Kurdish area in northeastern Iraq, which has been the most peaceful and prosperous part of the country for more than 20 years.

When the Islamic State militants overran the town of Sinjar on Sunday, the Yazidis immediately headed to the Kurdish areas, knowing they would find shelter there. The Yazidis who didn't leave in time are now stuck in the mountains.

For all the upheaval in Iraq, the relative stability of the Kurdish zone can be traced back to the sustained U.S. role there for many years. And — not coincidentally — to the Kurds, the most pro-American group in Iraq.

-- On the other hand, the mission announced by Obama bears similarities to the 1991 effort because Iraq as a whole remains mired in chaos. The rival ethnic and religious communities have never been able to live in harmony and the current crisis reflects the latest chapter in a long and painful history.

The imperiled Yazidis have repeatedly been at the mercy of more powerful forces and the only difference this time is that the international community has become aware of their plight.

When Obama withdrew the final U.S. forces at the end of 2011, the U.S. military had for more than two decades been active in Iraq on a daily basis, waging two wars and imposing the no-fly zone. Less than three years after that withdrawal, Obama is reluctantly returning to Iraq at a time when the country has fractured into three distinct zones — Sunni, Shiite and Kurdish — with no solution in sight.

Even as Obama announced the airdrops and airstrikes in northern Iraq, he emphasized that the U.S. was not making a broader commitment and offered no long-term strategy for sorting out Iraq's seemingly endless crisis.

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