It was a crackling summer skirmish between two old survivors of the 1960s, fighting about one of recent American history's ambiguities - the role of the Kennedys in a protracted, secret war against Fidel Castro's Cuba.

In it were Arthur Schlesinger Jr., former presidential adviser and author of a 1,031-page book on President Kennedy's years, pitted against Bill Moyers, the youthful spokesman in President Johnson's White House.

The controversy centered on a two-hour television documentary produced by Moyers and broadcast June 10 in CBS. It showed that President Kennedy authorized a covert war against Cuba after the 1961 Bay of Pigs invasion and appointed his brother, Robert F. Kennedy, to supervise it.

The program, which traced the long history of clandestine CIA activity involving Cubans before and after the Kennedy administration, was widely praised by critics.

But on July 5, Schlesinger wrote a blistering critique of it in a long, open letter to Moyers in The Wall Street Journal. Schlesinger charged that Moyers' history was "slipshod and polemical," and asserted that the program was "shabby and tendentious."

Regarding the assassination plots that were part of the overall CIA operation against Castro, historian Schlesinger said that "not a scintilla of hard evidence has ever emerged to show that Kennedy or Eisenhower for that matter authorized or even knew about the CIA murder plots."

Yesterday, however, Moyers fired his own salvo in the same space.

In doing that, he also disclosed a document in which Schlesinger counseled Kennedy to feign ignorance of the Bay of Pigs invasion cover operation if the invasion failed.

Schlesinger's advice was contained in a letter to Kennedy in April, 1961, after the President had authorized the invasion. At the time, Schlesinger was a special presidential adviser.

Under the heading, "Protection of the President," Schlesinger gave this advice, Moyers wrote:

The character and repute of President Kennedy constitutes one of our greatest national resources. Nothing should be done to jeopardize this invaluable asset. When lies must be told, they should be told by subordinate officials. At no point should the President be asked to lend himself to the cover operation. For this reason, there seems to merit in Secretary [of State Dean] Rusk's suggestion that someone other than the President make the final decision and do so in his absence - someone whose head can later be placed on the block if things go terribly wrong."

According to George Crile, who, with Moyers, produced the documentary, "The CIA's Secret Army," the Schlesinger letter was obtained earlier by columnist William Buckley.

President Kennedy did not take the advice of the prize-winning Harvard historian and, instead, publicly accepted personal responsibility for the Bay of Pigs disaster.

In his July 5 open letter in The Wall Street Journal, Schlesinger said that the secret activities against Castro after the Bay of Pigs were a "blot on the Kennedy administration," Moyers noted in his "Dear Arthur" response that there was nothing about the covert activities in Schlesinger's book on the Kennedy years, "A Thousand Days."

Schlesinger has recently completed a biography of Robert F. Kennedy, who was John Kennedy's Attorney General.

At the heart of the controversy is the ambiguity of Robert Kennedy's role in directing the CIA's secret operations, which included assassination plots commando raids on Cuba and other activities.

Schlesinger asserts that for most of the period the CIA was a "rogue elephant" which operated beyond the control of the presidency.

The Moyers program showed, however, that talks of assassinations was common at various levels of the government, and that presidential adviser McGeorge Bundy was briefed by the CIA's Richard Bissell about "executive action" - the agency's assassination capability.

Moyers explained to Schlesinger in the letter published yesterday that the CIA used circumlocutions in briefing presidents - a technique that left a President free to "plausibly deny" knowledge of specific operations.

Moyers disagreeing with Schlesinger's "rogue elephant" theory of CIA operations, said it seemed to him that the agency was operating "within the mores of that prevailing consensus in the high councils of government."

Although Moyers worked for the Johnson administration, he was also friendly with the Kennedys - so friendly, in fact, that Johnson once suggested that he was a member of the pro-Kennedy cabal in his administration. "Lyndon," a book by Haynes Johnson and Richard Harwood of The Washington Post, describes Moyers "dancing the Watusi" at parties at the Virginia home of the late Robert F. Kennedy.

Moyers wrote yesterday that Schlesinger's "deep personal attachment to the official view of reality in those years" distorted his response to the television documentary.

Moyers said his last conversation with Robert Kennedy, at New York's Caravelle Hotel, suggested that Kennedy himself was having serious doubts about some of the tactics of his late brother's administration.

"I have myself wondered if we did, not pay a very great price for being more energetic than wise about a lot of things, especially Cuba," Moyers quoted Robert Kennedy as saying.