The president of the Los Angeles World Affairs Council challenges critics of President Obama’s Ukraine policy by saying, “What are you going to do, send the 101st Airborne into Crimea?” Not exactly subtle. And rather silly, considering that no one has proposed such a thing.

The alternative to passivity is not war but a serious foreign policy. For the last five years, Obama’s fruitless accommodationism has invited the kind of aggressiveness demonstrated by Iran in Syria, China in the East China Sea and Russia in Ukraine. But what’s done is done. Put that aside. What is to be done now?

We have three objectives, in ascending order of difficulty:

Reassure NATO:

We’re already sending U.S. aircraft to patrol the airspace of the Baltic states. That’s not enough.

1. Send the chairman of the Joint Chiefs to the Baltics to arrange joint maneuvers.

2. Same for the four NATO countries bordering Ukraine – Poland, Slovakia, Hungary and Romania.

3. Urgently revive the original missile defense agreements concluded with Poland and the Czech Republic before Obama canceled them unilaterally to appease Russia.

Deter Russia in Ukraine:

1. Extend the Black Sea maneuvers in which the USS Truxtun is currently engaged with Romania and Bulgaria.

2. Declare that any further Russian military incursion beyond Crimea will lead to a rapid favorable response from NATO to Kiev requests for weapons. These would be accompanied by significant numbers of NATO trainers and advisers.

This is the “tripwire” strategy that’s been successful for half a century in Germany and Korea. Any Russian push into western Ukraine would then engage a thin tripwire of NATO trainer/advisers. That is something the most rabid Soviet expansionist never risked. Nor would Putin. It would, therefore, establish a ring of protection at least around the core of western Ukraine.

Reverse the annexation of Crimea:

Clearly the most difficult. In the short run, likely impossible. There are no military cards to play; Russia’s holding all of them. Ukraine’s forces are very weak. The steps must be diplomatic and economic.

First, Crimean secession under Russian occupation must lead to Russia’s immediate expulsion from the G-8. To assuage the tremulous Angela Merkel, we could do it by subtraction: All seven democracies withdraw from the G-8, then instantly reconstitute as the original G-7.

As for economic sanctions, they are currently puny. We haven’t even named names. We’ve just authorized the penalizing of individuals.

Name the names, freeze their accounts. But any real effect will require broader sanctions and for that we need European cooperation. The ultimate sanction is to cut off Russian oligarchs, companies and banks from the Western financial system. That’s the economic “nuclear option” that brought Iran to the negotiating table. It would have a devastating effect on Putin’s economy.

As of now, the Germans, French and British have balked, which means we can do nothing decisive in the short or medium term. But we can severely squeeze Russia in the long term.

How? For serious sanctions to become possible, Europe must first be weaned off Russian gas. Obama should order the Energy Department to expedite authorization for roughly 25 liquid natural gas export facilities. Demand all decisions within six weeks.

Second, call for urgent bipartisan consultation with congressional leaders for an emergency increase in defense spending. Nothing demonstrates American global retreat more than a budget that reduces the U.S. Army to 1940 levels.

Obama is not the first president to conduct a weak foreign policy. Jimmy Carter was similarly inclined – until Russia invaded Afghanistan. He responded boldly.

Invasion woke Carter from his illusions. Will it wake Obama?

Charles Krauthammer is a columnist for The Washington Post. He can be contacted at:

letters@charleskrauthammer.com