Nearly everyone at the book party for former ambassador U. Alexis Johnson last night was a Mr. Ambassador or an Honorable. It was the kind of event where the guests' combined experience is so great it threatens to crash through the floor with its weight.

"When he resigned," former U.S. Information Agency director Leonard Marks said of Johnson, "I took him to lunch and said, 'Alex, if you don't write a book, it will be a tremendous waste.' "

Johnson was ambassador to Japan, Czechoslovakia and Thailand, a U.S. coordinator at the Geneva Conference in 1954, undersecretary of state for political affairs during much of the Vietnam war and negotiator at the Geneva SALT talks between 1973 and 1977. He has seen, if not everything, a whole lot.

So Johnson, along with coauthor Jef McAllister, wrote "The Right Hand of Power: The Memoirs of an American Diplomat." The book begins: "American foreign policy is in trouble." America has lost its vision in foreign policy, they write, and go on to suggest that part of the solution would include longer presidential and congressional terms, a shorter and less arduous presidential campaign and more attention to history.

The 75 guests at the Cosmos Club included former diplomat Walter Stoessel and Alice Acheson, widow of the former secretary of state. Johnson told them, "I have a deep sense of the lack of a sense of history in the country, and the deep importance of imparting a sense of history."

Last night, a sense of history meant not being surprised when President Reagan announced yesterday that "I was responsible" for the recent bombing of the U.S. Embassy annex in Beirut.

"I think every president has had to do that," said Dwight Porter, ambassador to Lebanon from 1965 to 1970. "Anytime something like that happens -- it just has to be done."

A sense of history meant remembering Beirut long before there were truck bombs.

"When I was there it was quiet, but the divisions were there," said Raymond Hare, who served as vice consul to Lebanon in 1932 and ambassador from 1963 to 1964. Since those years, the life of a foreign service officer has become more dangerous, Hare said, not only in Lebanon, but "everywhere."

"You think about it, but you take it for granted," he said. "Danger, in a way, is always more awesome when it's far away. When it's right there, it's just a fact."

Porter said that, despite some threats while in the Middle East, he never worried about his or his family's safety.

"It was more psychological warfare then," he said. "The threats weren't real. I never had any cause for concern for my family -- I always sensed the Arabs respected women and children. Now, there's no sense of discrimination among the targets."

And a sense of history meant eagerly repeating the stories you grew up on.

"He was a prisoner of war in China, in 1942," said Brad Zerbe, the political director of the National Conservative Political Action Committee, of his grandfather, Johnson. "My grandmother [Patricia] didn't know if he was alive or dead. Somehow, he got to a shortwave radio. One day, she turned her radio on and his voice broke over the airwaves saying, 'If anyone hears this, tell Pat I'm alive.' "