Story highlights Rand Paul hits back at critics with a big foreign policy speech.

Paul outlines when he thinks the U.S. should use force in foreign entanglements

The Kentucky Republican is considered to be shaping a potential 2016 presidential run

For the first time since facing an onslaught of criticism this year over his foreign policy views, Sen. Rand Paul spelled out his national security principles Thursday in a comprehensive speech.

The Kentucky Republican, who's aggressively laying groundwork for a potential presidential campaign, sought to paint himself as a champion of "conservative realism," a doctrine that skates between the hawkish and dovish ends of the foreign policy spectrum.

"Yes, we need a hammer ready, but not every civil war is a nail," he said in New York at the Center for the National Interest, a think-tank founded by former President Richard Nixon.

"We need a foreign policy that recognized our limits, preserves our might and a common sense conservative realism of strength and action," he added.

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Paul attempted to address critics that characterize his views as isolationist and was aiming to approach his speech Thursday from the perspective of a major, would-be U.S. leader, rather than a lawmaker, a spokesman told CNN before the speech.

He sketched out how and when he would advocate for the use of force, saying he would only do so if he felt the United States or its interests were threatened. He said he supported the response to al Qaeda after 9/11, for example, but disagrees with the continued U.S. presence in Afghanistan.

"It's hard to understand our current objective. Stalemate and perpetual policing seems to be our mission now in Afghanistan, Iraq, Syria," he said. " A precondition for the use of force must be a clear end and a goal."

He went on to underscore his widely known position that a president should seek authorization from Congress before taking military action. Paul recycled his own criticism that President Barack Obama, "urged on by (former Secretary of State) Hillary Clinton," took action in Libya without approval, yet now the country is a "sanctuary for terror groups across North Africa."

"America shouldn't fight wars where the best outcome is stalemate. America shouldn't fight wars when there is no plan for victory. America shouldn't fight wars that aren't authorized by the American people," he said.

"America should and will fight wars when the consequences -- intended and unintended -- are worth the sacrifice," he continued. "The war on terror is not over, and America cannot disengage from the world."

He also talked at length about maintaining diplomatic relationships abroad and expressed support for using sanctions to underwrite diplomacy against countries such as Russia and Iran. And he reiterated a stance he has consistently taken: that the country's debt is one of its biggest national security threats.

His speech comes as he attempts to further distance himself from the more libertarian views trumpeted by his father, three-time presidential candidate and former congressman Ron Paul. With an eye on the presidency, Rand Paul has sought to broaden his appeal to establishment Republicans and even Democrats.

The attention has attracted close scrutiny of his views and past statements on foreign policy, as Paul has been known to frequently break with his own party and lean toward staying out of foreign entanglements. (Last month he slammed hawkish lawmakers for being "barnacled enablers" that have "never met a war they didn't like.")

He was widely panned this year when he evolved in his opinion about the crisis in Ukraine, as well as the threat of ISIS in the Middle East, as both situations continued to worsen.

On ISIS, for example, he penned an opinion piece earlier this summer openly questioning the value of launching airstrikes against militants in Iraq.

But not long after the beheading of American James Foley, Paul became supportive of a U.S.-led air campaign against the terrorist organization -- a change that critics made sure to highlight as a massive flip-flop but what Paul reluctantly admitted as a change in views based on the situation at hand, the "realist" side of his worldview.

Thursday night, he stressed his support for airstrikes as a way to "rebalance" the region but reiterated his opposition to another key part of Obama's strategy: arming Syrian rebels to fight ISIS militants.

He expressed doubt that ISIS will be dismantled in the future, saying in the end it will be up to the countries in the region to take care of the situation.

Michael Czin, press secretary for the Democratic National Committee, argued that Paul won't be able to overcome confusion about Paul's foreign policy with just one speech.

"For months, Rand Paul has been twisting in the wind, trying to explain his foreign policy vision," he said. "The fact is, a speech defending the indefensible won't make Paul's worldview any more palatable to the American people."