If you didn't live through it, you've probably seen it anyway - the defining picture of the Vietnam War of the last helicopter leaving our embassy in Saigon as the North Vietnamese overran the city.

Vietnamese who worked with Americans were absolutely desperate to get out of the country and this picture show that desperation in the most horrific way:

Is such a scenario possible in Baghdad?

The Iraqi army appears to have collapsed and it is unclear whether the government of Prime Minister Nouri al-Maliki can stop the ISIS terrorists from overrunning the capitol. If that were to occur, the US embassy in Baghdad - the biggest in the world - would be a prime target of the terrorists.

Richard Fernandez:

If the embassy is evacuated as al-Qaeda reaches Baghdad the optics will be atrocious. The very magnificence of the buildings will underscore the magnitude of the defeat. The sheer size of the palaces will make destruction no easy task. For these grand edifices, constructed at so much taxpayer cost must be reduced to total ash by America’s own hand.  The taxpayer pays for the matches.

As the US embassy in Saigon prepared to be overrun the incinerators were filled to overflowing with US dollars and classified documents. Liquor stores were smashed. In the event there was not even enough time to destroy everything. Yet by comparison the US Embassy in Saigon is hovel compared to the facility in Baghdad.

North Vietnamese troops as well as intelligence and army officials scoured the abandoned Embassy shortly after taking Saigon on the afternoon of April 30. Over the next several days, they apparently were able to piece together classified documents that had been shredded but not burnt and used these to track down South Vietnamese employees of the Central Intelligence Agency.

In the event Baghdad is overrun, one can only hope the rear guard uses enough C4 to leave not a stone upon a stone.  And thermite where appropriate.   Until it’s gone. All gone.

But great though the loss of the buildings will be, the blow in terms of intelligence gathering capabilities, networks, facilities and dislocation will be monumental. No one knows how many translators, sub-agents and locals who have risked their lives for the US will be left twisting in the wind. It will be no easy task to thoroughly efface the work of years. Yet it will have to be done if al-Qaeda is not obtain the greatest intelligence windfall of its career. President Obama may find a way to screw that up too, for even to be properly defeated requires a competence he may lack.

Baghdad has not yet fallen. It may never fall. But prospect should make people sit up and wonder whether they understand the meaning of the word “defeat”. It’s not just a word or military phrase, but a condition of unutterable loss and subjection. It is humiliation distilled. It is total abjection.

President Obama grew up in a generation which cheered “defeats” as comically grainy events on black and white film which took place in far away places.  Perhaps it had for them a quality of unreality. Some prank on The Man, a something happening to someone else. Let’s see how they like it in HD.

Some on the left may have wanted this image all along - coveted it, longed for it:The utter, total humiliation of the US would make them 2 for 2 in wars they opposed. And knocking American down a peg or two (or more) so that we're just like any other obedient servant to the international community would be gravy.

President Obama has rebuffed requests for assistance from the Iraqi government for months. No doubt he doesn't want to be dragged in to what amounts to a sectarian civil war. But sitting in the big chair sometimes means taking big risks. When you're a risk-averse president, however, no commitment of US forces will ever be justified. So you end up sitting in the White House bemoaning the state of the world without doing anything about it.

I don't want to see a last helicopter leaving from our Baghdad embassy. Whatever we can do to avoid that scenario, we should do it and do it quickly.