“Today I authorized the Armed Forces of the United States to begin a limited military action in Libya in support of an international effort to protect Libyan civilians.” That’s how President Obama opened Saturday’s briefing announcing his decision to launch a war in North Africa.

In a famous literary spat, Mary McCarthy said of Lillian Hellman, “every word she writes is a lie, including ‘and’ and ‘the.’ ” In the sentence above, Obama does somewhat better: “and” doesn’t appear, and the president’s on firm footing with his use of the definite article. But let’s just say that several key phrases here are, er … debatable:

• “An international effort”: “We did not lead this,” Secretary of State Hillary Clinton told reporters Saturday. But we are leading it. There are 11 U.S. warships in the region, just one each from the French and the Brits.

The entire operation is under U.S. command, and we’ve launched 110 Tomahawk missiles so far at more than $500,000 a pop. As usual, Uncle Sucker is doing the heavy lifting, and the “glory” — or, more likely, the blame — will be ours.

• “Limited military action”: Remember Gen. Colin Powell’s prudent guidelines for use of force, which he outlined in 1991 during his stint as President George H.W. Bush’s national security adviser?

Per Powell, before risking American blood and treasure, responsible leaders should identify, at a minimum, a vital national security interest, a clear and achievable military mission, and a sound exit strategy.

That was so ’90s. Today, we seem determined to keep proving Powell’s 2003 “Pottery Barn rule”: “You break it, you bought it.”

Obama is adamant that “we will not deploy any U.S. troops on the ground.” Yet in a Senate hearing last week, the Air Force chief of staff told Sen. John McCain, R‑Ariz., that “A no-fly zone, sir, would not be sufficient” to turn the tide. Indeed, the result could be a bloodier, more protracted civil war.

What then? How will that promote the president’s announced goal of “protect[ing] Libyan civilians”? Has anyone thought this through?

• “I authorized”: Most objectionable, of course, is Obama’s “decider”-like insistence that he alone has the power to commit the nation to a nondefensive war. Under our Constitution, this isn’t one man’s call — and Obama, a former constitutional law professor, knows it.

On the campaign trail in late 2007, he told reporter Charlie Savage that the president lacks the constitutional power “to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.”

Then-candidate Hillary Clinton said much the same: “The Constitution requires Congress to authorize war.”

It is “a great principle in free government,” James Madison wrote in 1793, “that those who are to conduct a war cannot in the nature of things, be proper or safe judges, [of] whether a war ought to be commenced.” The Constitution leaves that question to Congress.

Not that Congress is much interested. House Speaker John Boehner, R‑Ohio, announced his support for the airstrikes, but groused that Obama “must do a better job of briefing members of Congress” about the wars he starts.

We’ve heard a lot of chatter recently about whether the president looked “weak” by hesitating to jump into the Libyan civil war. Do we have to consider him “strong,” now that he’s caved in to the hawks and gotten us entangled?

In fact, it takes real strength of character for a president to exercise restraint — to uphold his constitutional oath of office and refrain from waging war when war isn’t necessary. By that standard, Obama has just demonstrated that he’s as weak as they come.