In the fourth year of his presidency, Jimmy Carter finally came under his baptism of fire.

No longer can the president make his proudest campaign claim: that no Americans died in combat during the Carter years. That fervent boast that had found its way into his reelection commericals now lies shattered in a desert halfway around the world, in the wreckage and carnage of an American helicopter and an American transport plane and the bodies of eight American servicemen who died in a military action before they could even get to the zone of combat.

Now Americans are moving into that stage of public response that has become all too familiar -- the post-tragedy public inquiry, conducted, like theater-in-the-round, for all to see and with no place for the principals to hide.

The focus, for many, will be upon Carter, a president already marked with an image of incompetence, some of it duly earned and some of it not. It has fallen upon Carter to have presided over the most recent of America's military failures.

But the most far-reaching of questions should be directed not at the president, but at the American military establishment that he nominally heads. The saddest fact of all, for those Americans who most love their country, is that the professionals of the American military have compiled a modern record replete with failure and catastrophe. It is a record that is a concern to all those, within this country and among allies, who must rely upon the U.S. military for their ultimate protection.

Just five years ago this week, the U.S. marked the epitome of this era of global humiliation, as Saigon fell to the communist forces. For years, Americans had been told that there was light at the end of the Vietnam tunnel; five years ago, sadly, Americans learned the light was red.

The fall of Saigon was a defeat for America's political and military leaders. But along the way, and in its aftermath, there was a long line of military failures, beginning with the just-100,000-more-troops-will-do-it reports of Gen. William Westmoreland. There was the military invasion of Cambodia to destroy COSVN, the purported headquarters for the communist forces in South Vietnam; the U.S. military came out claiming victory in the search for COSVN, but could produce little more than a few lead pipes to certify their effort.

There was the attack on the North Vietnamese prisoner of war camp at Son Tay, where U.S. troops staged a daring raid on what proved to be an empty box.

There was the rescue of the crew of the Mayaquez, an exercise in which 41 American servicemen lost their lives to save 40 American maritime crew members who were at that moment being released, anyway, by their cambodian captors.

And there was, before all that, the Bay of Pigs, a CIA production.

Now, with the aborted rescue effort in Iran, Carter joins his modern predecessors in the realization that a president, in his role as a commander in chief, is only as good as the professionals under him. And, although Carter is saying strongly that it isn't so, it seems clear from the debacle in the desert in Iran that he has been ill-served by the military he heads.

Carter undertook the daring rescue amid a sharp rise in American frustration over the crisis in Iran and plunging public confidence in the way he was handling it. Once, his patienceand willingness to work through diplomacy to solve the crisis had earned him highest marks from the American public. Now the polls were telling him that era was past. And while this is not presented to say that is why Carter decided to act militarily, in the sixth month of the crisis, it is the setting in which he made his fateful decision.

From the beginning, Carter had wavered in his public emphasis, threatening the use of force at one point, talking about his decision to forgo military action at another.

On Nov. 20, 1979 -- 16 days after the Iranian militants seized their American hostages -- the president first threatened the use of military force. aHe did it through diplomatic nuance, but his meaning was clear. the United States sought a "peaceful solution," he said: "this is far preferable to other remedies available to the United States. Such remedies are explicity recognized in the charter of the United Nations."

To make sure the meaning was clear, reporters were referred to Article 51 in the U.N. charter, which refers to a country's "inherent right of self-defense" in case of attack.

By December, the president and his officials were talking about efforts to resolve the crisis through diplomatic and economic pressures, without resorting to military force.

In February, the United States shelved its plan for economic sanctions, in hopes that a new, conciliatory atmosphere within the government of newly installed Iranian President Bani-Sadr would lead to release of the hostages.

But by April, with Iran having dashed all diplomatic efforts, Carter returned to the hard line. On April 17, announcing a new list of economic reprisals, Carter said that if these and allied pressures fail, "the only next step available that I can see would be some form of military action."

Through all that, the president was meeting with his top officials to review and revise plans for the dramatic rescue effort in Iran. he held four lengthy, detailed sessions during that period, and senior officials who attended say the president questioned in detail each aspect of the operation -- including the number of helicopters that would be used, the type of arms and equipment, how and at what point the mission might have to be scrubbed.

Now these same questions are being asked by the public and the press and the Congress, all in the name of post-mortem inquiry.

For Carter, the failed effort may have achieved one positive result. It may have convinced the public that he does not really deserve the latest label that has come to be his.

A few weeks ago, a headline writer for the Boston Globe wrote a line as a joke that found its way into print -- and it found its way into acceptance by many who felt it captured the essence of this president. "Mush From the Wimp," he wrote, and "Wimp" was the label that stuck.

But the plan that Carter was working on all that time was in fact bold and daring and even courageous. The public ought to come away from the effort and the ultimate inquiry with at least this thought: the "Wimp" label does not fit. Carter made his decision and ran his command, and the failure of execution cannot take away from that.

The president's decision -- although made on the merits of the situation -- is likely now to become part of the presidential campaign.This president's fight for reelection has been woven intrinsically throughout his struggle to preside. And Carter realizes it most of all.

On March 27, in a revealing interview with Meg Greenfield, editor of the editorial page of The Washington Post, Carter talked on the mix of military force and domestic politics. He said:

"I have a very real political awareness that at least on a transient basis the more drastic action taken by the president, the more popular it is. When President Ford expended 40 American lives on the Mayaguez to save that many people who had already been released, it was looked upon as a heroic action, and his statureas a bold and wise leader rose greatly. u

"This is always a temptation. But al of the action we have taken in answer to some very severe provocations like those in Iran and Afghanistan have been peaceful in nature. We have options: political, military, and economic. I've decided to use political and economic options and forgo the military options altogether.We've not had any loss of life during this administration because of people being sent into combat. It happens to be the first time in 53 years that has happened."

EPILOGUE: The day after the fateful decision to abort the rescue, one of the president's most senior advisors sat reviewing all that had gone wrong. Three helicopters malfunctioning out of a prized fleet of eight. A collision on the ground, with no enemy within miles.

"It's hard to believe," he said. "It seems like if ever a plan was snake -bit, this is it."

Later, another of Carter's senior advisers who worked on the plan pomdered the observation. The same, he said, might be said of the president.