Picture a seventh-grade classroom on Long Island in the first week of 1968 with the lights off and the radiators cold. Ice has closed half the roads, the buses have been trickling in since dawn, and twenty-two students sit in their winter coats doing arithmetic by whatever gray light the windows will give them. Somewhere above the ceiling tiles two enormous escaped rats are moving around, and taped to the walls of the hallway outside are photographs of the boy in the second row wearing yellow tights with white feathers on the back. Out on the road a bus grinds past with an eighth grader hanging off the rear bumper, riding it for fun. And three hundred miles up the coast, in living rooms exactly like the ones these students went home to, the evening news is about to open with a place called Khesanh. January is the month when Holling Hoodhood finds out that a crowd can change its mind about you overnight, and that the change has almost nothing to do with you.

By the winter of 1968 almost every American household owned a television set, and most families watched the news while they ate supper. The evening newscasts had stretched from fifteen minutes to a half hour in 1963, which left the networks ample room for film shot overseas. Vietnam filled much of that room, because reporters and camera crews could travel with American units into the field. Night after night the fighting became a routine part of an ordinary evening at home, which is why that conflict is remembered as the first television war.

The pictures, however, did not travel as fast as the words did. Camera crews shot film in the field, and the exposed reels had to be flown to Tokyo or all the way to New York before anyone could develop and edit them. A battle therefore trailed its own broadcast by a day or more. Alongside the film came numbers — weekly casualty totals and enemy body counts, released at the daily military briefing in Saigon that tired reporters nicknamed the Five O’Clock Follies.

Then came Tet. On the night of January 30, 1968, during a truce declared for the lunar new year, communist forces struck more than a hundred cities and towns at once, and the fighting reached the American embassy in Saigon. Officials called the broken truce an act of treachery, but the attackers were driven back with terrible losses, so by the measure of ground held the offensive failed. What viewers saw on their screens, though, looked nothing like the steady progress officials had been promising, and public confidence eroded within weeks. By March more Americans told pollsters that sending troops had been a mistake than said it had not.

No right or wrong — close the screen and tell someone nearby what happened in this part. Can’t find anyone? Tell yourself out loud. The moment you teach it, you truly understand it.