For the second time this year, President Obama has committed U.S. military personnel to distant battlefields, putting them in harm’s way pursuant – more or less explicitly – to what is known in UN circles as a “responsibility to protect.” The theory goes that the international community has a duty to intervene to prevent harm to innocent civilians.

As a practical matter, this new supranational dictate – known in UN speak as “R2P” – translates into a purported obligation on the part of the United States to use force, or at least make it available, whenever called upon by others to do so. (The only exception seems to be circumstances where we might actually have vital interests, in which case, naturally, the “international community” would generally deem such a U.S. intervention to be impermissible.)

R2P was essentially the animating principle behind the still-ongoing, U.S.-enabled NATO operation in Libya. We went in, as President Obama famously put it, because we had been “volunteered” by the Arab League and the UN for the mission of protecting civilians there.

Never mind that untold numbers of civilians have been killed, wounded or dispossessed in the course of the civil war that was abetted by that campaign – to say nothing of the fact that more there and elsewhere will likely perish at thehands of a government we have helped to bring to power, one that is dominated by the Muslim Brotherhood and/or al Qaeda.

Then last week, Mr. Obama advised Congress that he was dispatching 100 special forces troops to Uganda and three other Central African nations to protect civilians against the predations of Joseph Kony. Kony is the psychopathic cultist whose so-called “Lord’s Resistance Army” (LRA) is best known for its terrifying mahem, kidnappings, enslavement and military and sexual exploitation of children. His record has made him quite legitimately a public enemy throughout the region, sought for prosecution on war crimes charges by the International Criminal Court.

President Obama assures us that in both cases, U.S. military operations will be strictly circumscribed. In sub-Saharan Africa as in Libya, we will – in his immortal phrase, “lead from behind”: American special operations forces will not engage in combat, just train and direct the locals to put Kony out of business, much as we are still trying to help theLibyan “insurgents” do to Qaddafi.

The desire to protect civilians from the LRA scourge is understandable. After all, Kony is reportedly inflicting his predations in parts of four African nations with a relative handful of followers, by some estimates as few as 300. Some Republicans have joined Democrats on Capitol Hill in enacting legislation urging that he be brought to justice. And Kony’s abuse of children has certainly earned him a special place in hell.

The trouble is that we and our sometimes fractious African allies in any effort to end Kony’s reign-of-terror may or may not be able rapidly to achieve the stated goal, or at least do so with so few American troops. In any event, the opening of this new front comes at the same time the Obama administration and Congress are actively making deep and far-reaching cuts in U.S. defense capabilities.

The newly installed leadership of the Pentagon, Secretary of Defense Leon Panetta and Joint Chiefs Chairman Martin Dempsey, are the latest to warn legislators about the hollowing of our armed forces now underway thanks to roughly $465 billion in cuts already imposed by Team Obama. The breaking of our military – even without assigning it new missions – will become all the more certain if still-more-draconian reductions are made in the next few weeks. That will be particularly the case if the so-called “Supercommittee” charged with deficit reduction winds up triggering a massive, across-the-board reduction of some $600 billion more in Defense Department accounts.

Congress is on notice: Under such circumstances, we will not be able to maintain the forward presence and other power-projection capabilities upon which the nation has relied to protect its global interests and to keep the peace. Taking on additional overseas operations in distant theaters in the name of protecting innocent civilians only exacerbates that problem.

Unless and until the Obama administration and likeminded folks on Capitol Hill stop gutting our national defense capabilities, the use of the American militarybecomes what the political scientists call a zero-sum game: Personnel and equipment tied up in R2P operations in places like Libya or Central Africa – which means, of course, not just the troops and gear immediately engaged but the substantial logistical “tail” that supports the war-fighting “tooth” — are thereby made unavailable for other duties.

The larger question occurs: Mustn’t the first call on our shrinking armed forces be to fulfill our government’s responsibility to protect innocent civilians who happen to be Americans and their country?

This is not an academic question. At the moment, there is a grave and growing danger to both arising in Iran. The latest alleged Iranian plot to blow up targets in Washington, D.C. is but a foretaste of the kind of aggression that is in store for us and others when the mullahs finally get the Bomb.

Before Barack Obama dissipates any more of our military assets and capabilities with budget cuts and protecting innocent civilians elsewhere, he better take steps to protect our own against the threat posed by the Islamic Republic of Iran. The time to do that is now.