AND THERE they stood in an unswerving line, hands held proudly in the air, between the radicals and the police, trying to bring reason and peace to a violent confrontation. This was Saturday. This was the Justice Department in Washington. These were the New Mobe marshals.

They endured the taunts and obscenities of the militants-the Yippies, the Crazies, and, yes, the Mad Dogs. And while sticks and stones were hurled above and near their heads, they ringed the base of the Justice Department building and replied with the gesture that they and 250,000 other Americans had made famous that afternoon, the simple V.

Later, they were to receive a warm handshake from such Senators as McCarthy. McGovern, and Goodell, a condemnation from a distrustful Attorney General, and virtual accolades from even "establishment" newspapers like the Boston Globe. But now, in their most difficult test, they were alone, gallantly trying to save the peace that had been that afternoon.

"Give Peace a Chance," they had sung over and over on the vast grassy slope around the Washington Monument. "All we are saying is 'Give Peace a Chance, ' " sang the young college girl from New Brunswick, New Jersey, with a smile on her face and a woolly scarf around her throat. And they swayed in rhythm to the song-the marshals with arms linked ringing the speakers podium and keeping order in the crowd.

"Don't push," they urged the marchers so that there would be no panic in the crowd. And "keep on the inside of the white line." they kept reminding everyone as they marched down Pennsylvania Avenue.

At least one of the hairy radicals grumbled, "They look like third graders in a fire drill." But the marshals paid no heed.

THEY HAD trained long hours on how to keep the crowd quiet. There were 4000 of them. Many had worked the uphill trail of the McCarthy campaign, shining with the kind of hope that only youth seems capable of in the darkest hours.

And, now, they had stepped in to prevent the militants from turning the demonstration the Mobe had so carefully organized into a scene of senseless, polarizing violence. A young Mobe marshal moved down the sidewalk pleading with the crowd through his megaphone, "This is not an official Mobe demonstration. Will all those not connected with this demonstration please leave this area."

But as the militants continued to provoke the police, it became clear that the marshals had done all they could. A leader from the Mobe marshals conferred with the captain of the police. They looked out on the crowd. The Mobe marshal sadly shook his head.

Then with the authority and dignity of a man twice his age, he rode through the crowd on a motorcycle broadcasting, "All Mobe marshals step to the side." "God help us," he said.