Aleppo challenges President's legacy

"The United States did have countless opportunities to mitigate and prevent slaughter. But time and again, decent men and women chose to look away. We have all been bystanders to genocide. The crucial question is why."

Those were the words, a decade and a half ago, of author-academic Samantha Power in a seminal work exploring why "never again" -- a promise borne from the depravity of the Holocaust -- so often rings hollow.

This week Power -- now Obama's ambassador to the United Nations -- sat inside the Security Council chamber as world powers argued over this generation's iteration of Rwanda, Srebrenica and Guernica.

At least 300,000 people have died -- no one really knows how many -- in Syria's six year war, which is reaching a horrifying coda in Aleppo.

Power, like the White House, pointed the finger of blame directly at Damascus, Moscow and Tehran.

"The regime of , Russia, Iran, and their affiliated militia are the ones responsible for what the UN called 'a complete meltdown of humanity'," she told the Security Council.

"Are you truly incapable of shame?" she demanded. "Is there literally nothing that can shame you? Is there no act of barbarism against civilians, no execution of a child that gets under your skin, that just creeps you out a little bit? Is there nothing you will not lie about or justify?"

But the question is once again, how did it happen?

Syrian civilians may have been killed by Assad's loyalists, Russian warplanes and Iranian-backed militia. But for many, culpability lies at least in part at Obama's feet.

Legacy

From the president on down, US officials acknowledge that the slaughter in Syria will forever be a challenge to their reputations and their conscience.

"There hasn't been probably a week that's gone by in which I haven't reexamined some of the underlying premises around how we're dealing with the situation in Syria," Obama said in September.

But his administration bristles at the idea that they did nothing.

"I readily acknowledge that we are not seeing the results that we would like to see in addressing the violence inside of Aleppo," said White House spokesman Josh Earnest.

But, he added, "it's offensive to somehow suggest that the United States government and the world is not doing anything."

Throughout the slow motion destruction of Syria, Obama has believed that putting American boots on the ground would have been disastrous and establishing a no fly zone would have risked war with Russia.

Obama ignored his own "red line" on Assad's chemical weapons use, and faced down aides who warned that America's reputation would be severely damaged by inaction.

Faced with no substantial public pressure to act, the administration's mantra became: There is no military solution to the conflict in Syria.

For critics, that carries eerie echoes of Power's observations a decade and a half ago: faced with unspeakable violence, American officials often "spin themselves" to believe that US intervention would not work, or may even make things worse.

But events in Iraq, Afghanistan and Libya -- even Vietnam -- are seared onto the American body politic.

Instead of force, Obama decided diplomacy was the only way forward.

"I think that we have done, frankly, as well as you can do under the circumstances," Secretary of State John Kerry told reporters during a recent trip to Europe.

His repeated and vexed efforts to coax Russia into a deal to end the fighting were often ridiculed as Quixotic. Russia, critics said, had no intention of making a deal.

But Kerry, like the White House, believes it was worth a shot. "I'm not going to spend time regretting bona fide efforts to do things" he insisted.

Still, the White House knows that with power comes responsibility, and at the end of the day, Obama's even limited efforts failed.

"The United States has a special responsibility because we have the most influential, strongest country in the world," said Earnest. "We readily accept the responsibility."

Now, as Obama prepares to leave office, his opportunities to intervene in a meaningful way are dwindling to nothing.

All that is left is for the next generation's Samantha Power to adjudge whether and why "decent men and women" in Washington, once again, "chose to look away."