One is a Mossad spy turned diplomat who brilliantly expounds Israeli foreign policy in the clipped English of his native London. Another is a pudgy Iranian-born Israeli arms merchant with a taste for fat Havana cigars.

A third is a Connecticut-born engineer who founded Israel's booming aircraft industry and turned to arms dealing after retirement. And the last is a young war correspondent who rose through politics to become counterterrorism coordinator for five Israeli intelligence services.

Together, they braided the intricate cord that established U.S. contacts with the ayatollahs' Iran and made it possible for President Reagan to ship tons of American weapons to Tehran. The outcome has plunged Washington into its most searing scandal since Watergate.

Scores of question marks still swirl around their activities: Did they sell Israeli arms to Iran, separately from the Reagan initiative? Did they pocket some of the juicy profits from the U.S. sales? Were they aware that an American official was secretly slipping some profits to Nicaraguan rebels?

The facts known about their activities tell a story of lofty geopolitical strategy mixed with pragmatic foreign policy and hard-driven arms deals negotiated amid the opulence of some of Europe's best five-star hotels.

The facts also provide important information about how the Iranian arms shipments began, what the motivation of U.S. officials might have been for dealing with the Iranian regime, and how Israel, trying to help an ally for humanitarian reasons, became involved in a scandal that could affect congressional support for this Mideast country.

MOSSAD VETERAN

When in 1980 David Kimche became director general of the Foreign Ministry, the ministry's No. 2 man, he was already a strong advocate of making an extra effort to maintain the best relations possible with non-Arab nations that shared borders with Israel's Arab enemies.

Kimche, then 52, had just ended 20 years with the Mossad, Israel's CIA, where his last position had been deputy commander in charge of Africa. From that post, he had watched the non-Arab nations to the south of Egypt, Libya and Algeria. Now his vision broadened to include nations to the north and east.

He is said to have strongly supported Israel's 1982 invasion of Lebanon as a way of propping up Lebanon's Maronite Christian rulers. He improved Israeli relations with Turkey, which shares a border with Syria. And from the beginning, he lobbied for an overture toward Persian Iran, on Arab Iraq's eastern frontier.

Many people believe that Kimche was the prime mover behind Israel's policy since late 1980 of secretly selling weapons to Iran for its stalemated war with Arab Iraq. The total price tag has been put at a low of $500 million and a high of $5 billion.

According to news reports, Kimche, a London-born Ph.D. in Middle East affairs, tried in 1981 to enlist U.S. officials in his efforts. Kimche proposed that the United States try to re- establish contacts with moderates in Iran. The United States had broken relations after the seizure of the U.S. Embassy in Tehran by Moslem fanatics in November 1979.

The conservative army that had served Shah Mohammed Reza Pahlavi before his ouster in the 1979 revolution still was largely in place, Kimche argued, and should be helped so that it could topple Ayatollah Ruhollah Khomeini or get in line to succeed the aged leader when he died.