President Obama sent 1,000 Air Force Academy cadets into active duty Wednesday by laying out his vision for a postwar America in which the United States leads beyond the battlefield and defiantly challenging his critics’ notion of waning American influence.

In a commencement address to the graduating service members, Obama hailed a milestone moment as the country winds down its military involvement in the two wars that have defined the generation that has come of age after Sept. 11, 2001.

The Class of 2012 is the first in nearly a decade, Obama said, that is entering active service with no U.S. troops fighting in Iraq and the first that can envision an end to the Afghanistan conflict.

“For a decade, we have labored under the dark cloud of war. Now, we can see the light of a new day on the horizon,” the president said, speaking on a stage in the middle of the academy’s football field as the cadets, dressed in blue-and-white uniforms, sat in rows before him. “The end of these wars will shape your service, and it will make our military stronger.”

Obama’s appearance came just two days after he presided over a NATO summit in Chicago at which the allied nations agreed to a framework to wind down the Afghanistan war by the end of 2014. Over the past half-year, the president has touted the end of the Iraq war and the drawdown in Afghanistan as centerpieces of his foreign policy record as he makes his case for reelection, reminding the public that he made good on his campaign promise to end the Iraq conflict.

The Obama campaign has identified military families as a potential source of votes in battleground states, hoping to undercut a traditionally strong voting bloc for Republicans. Vice President Biden is scheduled to speak at West Point’s graduation ceremony Saturday.

The president used much of his speech Wednesday to declare that American influence has not waned, as some of his critics have suggested. Instead, he argued, “the United States is leading once more. From Europe to Asia, our alliances are stronger than ever.”

He pointed to the partnership with Japan after the earthquake and tsunami there last year and his administration’s approach to aiding Libyan rebels in overthrowing the oppressive regime of Moammar Gaddafi last fall.

The argument was aimed squarely at sharp criticism from the presumptive Republican presidential nominee, Mitt Romney, who has called Obama too soft on Iran. Republicans also have accused the president of responding too slowly to the pro-democracy movements that have challenged long-standing autocracies in the Middle East and North Africa, and failing to act decisively enough to end Syrian President Bashar al-Assad’s brutal crackdown on dissent.

“As we’ve done the work of ending these wars, we’ve laid the foundation for a new era of American leadership,” Obama said. “Let’s start by putting aside the tired notion that says our influence has waned, that America is in decline.”

As some have questioned whether he subscribes to the notion of American exceptionalism, the president pointedly used those very words.

“Never bet against the United States,” he said, adding that “the United States has been, and will always be, the one indispensable nation in world affairs. This is one of the many examples of why America is exceptional.”

Obama even repeatedly employed the same phrase, “American century,” that Romney used in a speech at the Citadel in South Carolina last October.

“I see an American century because of the character of our country — the spirit that has always made us exceptional,” Obama said. “It’s that simple yet revolutionary idea — there at our founding and in our hearts ever since — that we have it in our power to make the world anew, to make the future what we will.”

His appearance at the Air Force Academy kicked off a two-day road trip that will take Obama to three states — California and Iowa are the others — where he will hold four campaign fundraisers, a grass-roots event in Iowa and an official White House event where he will push Congress to support a tax credit for clean energy.

After his commencement address, Obama flew to Denver for his first fundraiser, at which he delivered an extended critique of Romney’s vision for improving the economy.

The Obama campaign has been criticized by Republicans, and some Democratic allies, for attacking Romney’s experience as the head of Bain Capital, a private-equity firm. But the president and his advisers say Romney’s time in the private sector is fair game because the former Massachusetts governor has touted it as a reason he is prepared for the presidency.

At the fundraiser, Obama said Romney should “be proud” of his success, but he added that his rival gleaned the “wrong lessons” from his experience. Romney wants to maximize profits for chief executives and cut taxes for the wealthy, Obama argued, and that’s “not a recipe for broad-based American growth.”

“Governor Romney says his 25 years in the private sector gives him a special understanding of how the economy works,” the president added. “If that’s true, why are they running around with the same bad ideas that led the economy to collapse last time?”