Naval vesselsU.S. NavyMembers of the Wall Street Journal editorial board want the U.S. to "deploy ships from the Europe-based Sixth Fleet into the Black Sea, and send the newly commissioned George H.W. Bush aircraft carrier to the eastern Mediterranean." Their counterparts at the Washington Post fault President Obama because he thought he could "radically reduce the size of its armed forces," but say he could "play a leading role" if he's forceful enough. Senator John McCain wants, "President Obama to rally our European and NATO allies." And House Speaker John Boehner insists, "At what point do you say enough is enough? We are at that point." We're at that point all right—of realizing that there are limits to what even a superpower can do when a nuclear-armed thugocracy like Russia decides to go romping, again, in one of its traditional playgrounds.

Sixth Fleet? Really? Is Russia supposed to believe that the United States is going to war to preserve Ukraine's independence? Do the pundits drawing a line want us to go to war to preserve that independence?

Ukraine has a long and storied history, marked in part by the need to draw its borders on maps in pencil. Surrounded by powerful and quarrelsome neighbors, it has been carved up by...everybody. It's even been carved up by its own people, in a flurry of mayflie-lived states that briefly filled the vacuum left by the collapse of the Austro-Hungarian Empire and the Russian Empire.

In the modern world, Ukraine has the misfortune to share a 1,400-mile border with an increasingy assertive Russia, led by a cartoon of a strongman, and a warm-water naval port with Russia's Black Sea Fleet. It's also heavily dependent on its neighbor for natural gas and owes Gazprom, the Russian state gas monopoly, $1.55 billion.

Which is to say, Vladimir Putin and Russia have a lot of leverage in Ukraine, short supply lines. and military forces already in place.

The United States is in a position to wag its fingers, perhaps impose some sanctions, but faces very real limits on the credibility of its demands and threats. No matter how powerful the U.S. military may be, any promises the U.S. makes to the Ukrainian people as they face down some of the world's worst neighbors are going to be hollow and false. American officials can't—and shouldn't—make promises that they're in no position to keep. Hollow assurances may lead Ukrainians to assume that they'll get backing that won't materialize—just as many Hungarians felt betrayed after NATO (understandably) failed to intervene to support the 1956 uprising despite encouraging pro-freedom rebels through Radio Free Europe and other official media.

Even worse would be the U.S. actually getting involved in the conflict, though even uber-hawk McCain concedes "there is not a military option."

Whatever happens in Ukraine depends primarily on the ability of Ukrainians to defend themselves and their independence. History isn't encouraging on that point, but Ukraine isn't defenseless, either.

But the United States isn't in a position to correct all the wrongs of the world. We look foolish when we can't back up our words, we might lead people to expect what can't be delivered, and we risk being drawn into conflicts in which we're at a serious disadvantage.

Taking a non-interventionist position recognizes the limits the world imposes on even the most powerful players. It may not be pleasant to have to watch events play out—but it's better than making them worse.