If one of the world's leading authorities on peacekeeping - Gen. Indar Jit Rikhye - is correct, much of the responsibility for the recent deaths of some 219 marines in Beirut must be placed on a basic misunderstanding of peacekeeping on the part of the United States government.
According to General Rikhye, ''Defending one's own position is permissible to a peacekeeping role, but US troops became increasingly involved in supporting Lebanese Army forces, largely dominated by the Christian Phalange faction, in their fights with other factions.''
He added, ''The multinational forces were from the start invited by a president (Amin Gemayel) whose constitutional authority was shaky and who himself was a Phalangist leader.
''Thus, US and French forces in Lebanon lost their peacekeeping role and became just another faction in the Lebanon civil war,'' he said.
General Rikhye emphasized that once the US removed itself from the peacekeeping role by becoming a participant in the conflict, it had to act like a participant and do a proper job of defending its troops. Instead, the marine contingent in the multinational peacekeeping force was left largely unprotected and exposed to the whims of any one of the groups whose enmity it had gained.
Rikhye, a heavyset, courtly man, has dedicated the past 26 years to peacekeeping. He has led peacekeeping forces in the Middle East and Congo, and served as the principal military adviser to UN Secretaries-General Dag Hammarskjold and U Thant. He headed the UN forces in Gaza in June 1967 when they were asked to withdraw by then Egyptian President Nasser. It was a move which preceded the 1967 six-day war between Israel and Egypt.
In 1969 he left the UN to start the New York-based International Peacekeeping Academy, which is dedicated to training diplomats and Army officers in multilateral approaches to peacekeeping and conflict resolution.
The general bears a strong imprint of the two professions in which he has spent most of his life. His unmistakable air of military authority intertwines with the highly developed charm and reluctance to offend of the professional diplomat.
Turning to the security arrangements at the US marine headquarters in which the soldiers were killed, he said, ''It's very easy to be wise after the event and particularly after this huge loss of life. I think that the situation demanded a different type of deployment and billeting, with the still fresh experience of the bombing of the US Embassy (very similar in execution to the assault on the Marine installations). And the attacks on the French Embassy. There was a lesson that these and similar installations were easy targets.''
Breaking into a more emotional tone, he said, simply, ''I am shaken by this tragedy, a man like me can take losses very easily, but these I call unnecessary losses - the truck got right in.''
Rikhye continued, ''From what I read in the paper I am surprised at how a vehicle was able to go through the checkpoint after the attacks of the past few months. One would expect there would be special precautions.''
Rikhye speculated about what had led the US to commit these errors. ''I'm not sure why they behaved as they did. Was it because they believed that no one would dare attack United States troops? Or did their false sense of security come from the fact that they had proved in recent bombing attacks against Druze and Shiite positions that they possessed enormous firepower and could hit hard whenever they so chose? Did they over-rely on this show of force and think that it would discourage anyone from attacking them?''
''Or,'' said Rikhye, ''did they really believe that they were still only peacekeepers and that the occasional attacks they made on the positions of several Lebanese factions would not have any real consequences?''
Asked if the Reagan administration seemed to have coherent policy goals when it sent the forces into Lebanon, Rikhye repeated the administration's stated goals of separating the combatants, creating a good climate for negotiations, and achieving Syrian and Israeli withdrawal. He added, however, that the US did not have a long-term policy to bring about the withdrawal of Syrian and Israeli forces. ''No US government, given the nature of US politics, can make long-range policy. This is hard for any democracy, and particularly one under your system, where you have to constantly reflect the impact of domestic politics on foreign policy, and in no other country is foreign policy so affected by political concerns as it is in the US,'' he said.
Rikhye said it would be too damaging to US national prestige to withdraw the Marines right away. But, he said, in the long run a UN peacekeeping arrangement in Beirut would be the best arrangement.
Looking at the larger picture, the general stated, ''The primary US role remains that of being the main negotiator in: (1) bringing about reconciliation between the warring parties, and (2) achieving the withdrawal of foreign forces. In its attempt to achieve the first goal it already has the support of the Saudis. It now needs to get the support of other countries, notably Syria.''