Yesterday's speeches by world leaders at the United Nations are bringing into focus some of the most pressing and bedeviling questions of our time. How much can we do to affect a situation in Syria that is further destabilizing the Middle East? How much are we willing to do? And can we, our allies or our enemies ever accurately foresee the effects of such meddling?

In Syria's civil war, 250,000 people have been killed and 10 million displaced. Images of slaughter and refugees are heartbreaking. The United States has attempted in a very limited way to support the forces that oppose Syria's leader, Bashar Assad, but also oppose the Islamic State forces that are Assad's main enemy. The effort has yielded little.

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We learned on Sunday that Russia, which has been working to support the Syrian government, has entered into an intelligence-sharing agreement with Iran, Iraq and Syria. President Barack Obama told the UN General Assembly Monday that after so much bloodshed and conflict, Syria can't return to the prewar status quo. But that appears to be what Russia and its Middle East allies seek, and their commitment far outstrips ours. Jordan's leader told the UN his nation needs help handling a flood of Syrian refugees. Russia and Iran's leaders put the defeat of the Islamic State above any other concern in the Syrian conflict. So it's not surprising that Obama's private meeting with Russian President Vladimir Putin was a chilly one. Obama is at odds with Putin, whose nation the United States has already laid sanctions on for its aggression in Ukraine and Crimea.

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Obama was elected in 2008 in large part for his promise to get us out of Iraq and Afghanistan. What he has since tried to do is maintain our power in the world via diplomacy, with minimal military involvement. Not surprisingly, the effect has been minimal, particularly where other nations are willing to do and risk more. Obama's long-term strategy is likely to be the one most beneficial for the United States, but may well be bumpy and painful and risks criticism that we are sitting on the sidelines. There is every chance aggressive U.S. military involvement in Syria would lead to another Iraq- or Vietnam-style quagmire.

If Putin has forgotten the Soviet Union's misadventures in Afghanistan or wants to repeat them, that's his folly. Nations find stability when the strongest force, and the one that has the most backing of the people, gains power. Repressive regimes that are unpopular will eventually be challenged. Outside force often perverts the evolution of this process.

Neither ISIS nor Assad is a worthy ally. The horrible nature of one does not change the horrible nature of the other. We can weep for the dead there, and mourn for the refugees, and do quite a lot more to help them. But history suggests we can't make Syria stable. And even if we could through a massive military commitment, there is little hunger among the American people to sacrifice lives and money for this purpose. It can be difficult to do little. But when the potential outcomes are so uncertain, there is no good argument for militarily doing more.