by William Broyles, Jr.; Knopf; 284 pages; $17.95.

In 1969 William Broyles was a young Marine lieutenant fighting the Vietcong. He lived through it, came home, and in time got to be editor-in-chief of Newsweek . The war was far behind him. But he found it wouldn’t let him rest; he had left something in the bitter hills south of Da Nang, and fifteen years later he went back to find it. For a month he traveled through Vietnam—three thousand miles by car and jeep, ferry and sampan. On the way he spoke with hundreds of people: Communist party officials, soldiers who had fought him, mountain tribesmen, men and women who kept the supplies flowing over the Ho Chi Minh Trail, somebody who had survived My Lai, somebody who had survived the far less publicized Vietcong massacres.

He wanted to find out what sort of people he had gone to war against, what their experience had been, what we had left behind in their country (little enough —some rusting war machinery, and the Amerasian children whose features will be our most enduring legacy in Vietnam), and how a peasant society managed to stand up for year upon year against B-52s and Huey gunships. In the end he learned a great deal, as we do from his superb record of the journey. Part military memoir, part travelogue, part elegy for the dead of both sides and informed throughout with coolly expressed passion, Brothers in Arms is as fascinating as it is moving.