Armies plan carefully and train to fight with precision and discipline. But once the shooting starts, and the fog of war rolls in, all bets are off.

That's important to bear in mind as President George W. Bush ponders his next move in Georgia, where the stakes are high, the military situation fluid and American options severely limited.

On Wednesday, Bush dispatched Air Force planes carrying relief supplies and a military "assessment team" to determine what additional help is feasible. A high-ranking Pentagon official told The New York Times that the mission was designed "to show Russia that we can come to the aid of a European ally and that we can do it at will, whenever and wherever we want."

Russia's response was swift and blunt. President Dmitri Medvedev told the leaders of two breakaway Georgian regions on Thursday that his country would act as their protector "in accordance with the U.N. Charter."

Bush had demanded that Georgia's sovereignty be respected. Russian Foreign Minister Sergey Lavrov dismissed the idea. "One can forget any talk about Georgia's territorial integrity," he said.

Militarily, at least, there's isn't much the United States can do about it.

Bush is right to stand up for the democratically elected government of Georgia. The Russian incursion is designed to intimidate not only that country, which has been forging closer ties with the West, but also other former Soviet republics such as Ukraine that have followed similar paths toward free and open societies.

And the fact that U.S. military options are limited does not mean that America can do nothing. It is unlikely that Russia can be isolated the way Iran or North Korea have been. But NATO and our European allies have plenty of ways to punish Russia for its aggression.

The United States and its allies, for example, could organize a boycott of the 2014 winter Olympic Games scheduled for the Russian city of Sochi on the Black Sea near the border of Georgia. The West also could ostracize Russia from key cooperative international economic groups.

To his credit, Bush realized the urgency of diplomatic outreach, dispatching Secretary of State Condoleezza Rice to Paris and Tbilisi, Georgia.

Meanwhile, Secretary of Defense Robert Gates met with reporters, warning that the Russian incursion could harm relations with the United States "for years to come." But Gates also said that he sees no prospect of American military action.

It may be obvious to us in the West that the United States has no plans to intervene militarily in Georgia. But Russian military commanders in combat on the ground probably would regard it as unwise to take that for granted.

American troops have traveled to Georgia regularly over the past five years. More than 1,000 U.S. Marines and soldiers participated in joint training exercises with Georgian troops in late July. Former soldiers from Israel, a key U.S. ally, assisted.

Complicating the military situation are Russian-backed militias roaming the breakaway regions. They could act as surrogates at the direction of Russian operatives, or they may act on their own.

With fluid battle lines and sporadic fighting, the presence of U.S. troops in even limited numbers increases the risks that mistakes or miscommunication can cause an unintended and unwanted escalation.

Before she left on her diplomatic mission, Rice — an expert on the former Soviet Union — warned Russian officials that things have changed. "This is not 1968 and the invasion of Czechoslovakia, where Russia can threaten a neighbor, occupy a capital, overthrow a government and get away with it."

One thing that hasn't changed, however, is the power of Russia's conventional forces on the ground. That makes diplomacy, patience and a great deal of caution the only sensible responses for now.

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