President Reagan, former national security advisers John M. Poindexter and Robert C. McFarlane and former White House aide Oliver L. North have had difficulty remembering details of a Nov. 25, 1985, Israeli arms shipment to Iran, a transaction that has emerged as a focus of the cover-up phase of the Iran-contra affair.

Those officials claimed forgetfulness about details of that shipment when questioned last November, even though their involvement was recorded in an extensive trail of documents and witnesses.

Beginning on Nov. 17, 1985, Poindexter, then deputy director of the National Security Council staff, supervised the Washington activities of his subordinate, North, in support of what ended up as a Nov. 25 shipment of 18 U.S.-made Hawk antiaircraft missiles by Israel to Iran.

The original plan called for four more planeloads, for a total of 80 Hawks, and release of the American hostages then held in Lebanon. It was a plan that never worked out, according to released documents and testimony before the congressional committees investigating the Iran-contra affair and the Tower presidential review board.

The Israelis, who notified McFarlane and gained his approval before the shipment, had initially planned to carry it out on their own, but ran into difficulties. Poindexter and North were brought into the process of seeking U.S. assistance for the clandestine, high-risk operation.

During their efforts to expedite the shipment, Poindexter and North sought help from McFarlane (then in Geneva with Reagan), retired Air Force major general Richard V. Secord, officials at the Central Intelligence Agency, the State Department and the Pentagon, CIA and State Department officers in Lisbon and officials in the Portuguese government.

Records and testimony show that Reagan was told of the arms shipment at least three times during that period. On Nov. 18, while Reagan was in Geneva for a summit with Soviet leader Mikhail Gorbachev, McFarlane told him that the Israeli shipment was to take place and the hostages were to be freed Nov. 22.

On Nov. 25, with McFarlane away, Poindexter told Reagan at the regular 9:30 a.m. intelligence briefing that the shipment had finally gone to Tehran and the two hostages initially expected to be freed Nov. 22 may be released (they were not).

Poindexter's cryptic note going into that meeting read: "Hostages -- 1 to Tehran 22 {followed by an arrow} 2."

North's spiral notebook for those days contain many pages of entries relating to his activities on behalf of the Hawk shipment, including many references to CIA assistance to the operation.

An entry for Nov. 26, reflecting a talk with Poindexter, states, "RR directed op. proceed," shorthand for "Ronald Reagan directed the operation to proceed."

On that day, the CIA sent Poindexter a draft intelligence authorization, called a "finding," that retroactively covered the CIA's participation in the shipment, as well as the agency's preparations to help in another transaction later in December.

In the days that followed, CIA Deputy Director John A. McMahon regularly called Poindexter to make certain the finding was signed by the Reagan.

On Dec. 5, at Poindexter's first daily briefing of the president after he was named national security adviser, the first item on his agenda was to ask the president to sign the finding. As drafted by then-CIA General Counsel Stanley Sporkin, the finding also contained a special provision directing then-CIA Director William J. Casey to withhold informing Congress of the operation as required by law.

This in itself must have been a memorable event, since there has been testimony that was only the second time such a provision cutting out Congress had been written into a finding during the Reagan presidency.

Poindexter, apparently recognizing the unique and sensitive nature of the document, said he put the only copy in his NSC safe, rather than in the NSC secure file for sensitive documents, and passed word to the CIA that it had been signed.

On Dec. 7, two days later, Poindexter attended what he has described as a memorable, "free-wheeling" discussion in the White House residence, at which the president listened. The subject was future steps in the Iran initiative. One subject was another Israeli shipment scheduled for later that month, and Poindexter testified it was probable that past activities had been reviewed.

Attending were Secretary of State George P. Shultz, Defense Secretary Caspar W. Weinberger, White House chief of staff Donald T. Regan, McMahon, McFarlane and Poindexter. He remembered the meeting, Poindexter testified, but recalled little of what was said.

House and Senate committee members expressed skepticism last week that Poindexter, a man whose mental capacities were legendary when he served at the Pentagon, would have forgotten the November 1985 episode a year later, as he has testified he did.