Younger Americans don't know enough about the nation's history to appreciate fully the freedoms its military is defending in the war against terrorism, Lynne Cheney said Saturday.

Using a historical example more than 200 years old, she said George Washington's surprise Christmas Day attack on Hessian forces manning the British fort in Trenton, N.J., shows that freedom "is not our inevitable heritage."

"The founders had the odds stacked very much against them," the wife of Vice President Dick Cheney told a gathering of conservative activists.

"No one had ever thrown off a colonial power before. No one had ever established representative government across a vast expanse of land. The Americans were going up against the mightiest military force in the world."

The realization that freedom wasn't inevitable should make it "all the more precious to us. Were we to lose it, liberty might not come our way again," she said in a 20-minute speech closing out the Conservative Political Action Conference.

Mrs. Cheney, a senior fellow at the American Enterprise Institute, a conservative think tank, has long been outspoken about the lack of historical knowledge.

She said more than half of college seniors surveyed in 1989 did not understand the purpose of the Federalist Papers.

In a 1999 survey of seniors from elite colleges such as Princeton, Yale and Stanford, only one-fifth knew that the words, "government of the people, by the people, for the people," came from Abraham Lincoln's Gettysburg Address, Mrs. Cheney said.

Also in that survey, 40 percent of seniors did not know the Constitution divided power between the states and the federal government, she said.

"We haven't done a good job of teaching our history. We haven't given young people the knowledge they need to appreciate how greatly fortunate we are to live in freedom," said Mrs. Cheney, who has written extensively on the subject.

She recommended "teach-ins" — on college campuses, in public libraries and at private homes — as a way for Americans to learn more about the nation's history.

"So it's time for gatherings of a new kind, it seems to me, in which we remind ourselves of exactly what it is we are defending, in which we talk about exactly what it is we have at stake," said Mrs. Cheney. "Let's talk to one another about freedom."

Harkening back to the terrorist attacks of Sept. 11, "that awful day that changed so much," she said Americans are living in a moment that historians will write about forever.

"And I know that you like me are immensely grateful that we have, leading us through these times, our president, George W. Bush," Mrs. Cheney said.

She jokingly added: "And without any hint of bias, let me observe that the vice president is no slouch either."