"The burdens of this century cannot fall on American shoulders alone," the commander in chief said at the U.S. Military Academy, where in December he announced he was sending 30,000 more troops to Afghanistan.
Mr. Obama said the fight against al Qaeda, begun under President George W. Bush after the attacks of Sept. 11, 2001, is part of an international effort that was necessary and just.
"The threat will not go away soon," President Obama told the nearly 1,000 cadets seated on the field at Michie Stadium. "But let's be clear: al Qaeda and its affiliates are small men on the wrong side of history."
Complete Text of Obama's Speech at West Point
America, he said, has a history of not acting alone - citing World War II and the Cold War as among more recent examples.
"We are the United States of America. We've repaired our union, faced down fascism and outlasted communism," he said. "We have gone through turmoil and come out stronger, and we will do so once more."
President Obama said that although the nature of the war in Afghanistan has changed since it was launched late in 2001, it remains as important as it was in the days after Sept. 11.
"There will be difficult days ahead," he said. "But we will adapt, we will persist and I have no doubt that together with our Afghan and international partners, we will succeed in Afghanistan."
As Mr. Obama focuses on defeating a resurgent Taliban, some U.S. allies are questioning their commitment in Afghanistan.
In February, the Dutch government collapsed after Prime Minister Jan Peter Balkenende tried to meet a NATO request to keep the Netherlands' 2,000-strong contingent in Afghanistan from coming home this year. A majority of the Dutch parliament backed a withdrawal this summer, as planned.
The Dutch crisis, and growing public opposition to further involvement in Afghanistan, have fed fears that other NATO nations could rethink their role in the 8-year war. Canada, which serves in the same southern region as the Dutch, also plans to remove its 2,800 troops by next year.
Nearly the entire graduating class of 2010 will become Army second lieutenants, with most expecting to serve eventually in Iraq or Afghanistan, a fact that that President Obama said "humbled" him.
"I assure you you will go with the full support of a proud and grateful nation," he said.