The Greatest Generation is tired. In their day, with hearts clanging in their skinny, young chests, they flew bomb runs, manned the machine guns on 7,000 cargo ships or survived 124 days in a foxhole on an Italian beach surrounded on three sides by German troops.

Now, it takes all that a citizen soldier such as Eugene Lafferty has to climb the stairs at the National Air and Space Museum's Steven F. Udvar-Hazy Center. One by one, the 81-year-old widower labors up the steps with his cane. "I'm about out of steam," he said this weekend at his unit's reunion. They are old, their faces marked with wrinkles and age spots, and the once-easy gait of young men who didn't know any better has become the stiff, cautious step of old men who have seen too much.