A year ago, I stood in the streets of Beirut, talking with ordinary Lebanese as they celebrated the departure of PLO guerrillas, the election of Bashir Gemayel as President, and their hopes for peace at last after more than a decade of communal strife inflamed by Arafat's gunmen and Syrian troops. Beirut was on the verge of regaining its role as a prosperous center of culture, finance, and communication in the Middle East.
Today, the hopes are dashed and Lebanon is a mess. The President elected a year ago was assassinated, the government of his brother-successor teeters near collapse and American soldiers are being killed and maimed on foreign soil for the first time in many years. Today, instead of having been humiliated and ousted as an influence in the region, Russia has massively rearmed Syria and holds a tight grip on the Syrian Army with ''advisers'' down to the battalion level. The Soviets have deployed SAM-5 missiles, manned exclusively by Russians and command-linked directly to the Soviet nuclear-missile network in southern Russia.
A year ago, with the PLO'S military apparatus facing elimination and Russia's military equipment and political support of its radical clients discredited, the Reagan administration leaped in. Instead of backing our Israeli and pro-Western Lebanese allies, Ronald Reagan, like his predecessor, succumbed to the hubris that ultimately plagues provincial politicians suddenly thrust on the world stage. Overeager, quick to assert itself, and with a zeal uncomplicated by any depth of understanding of the historical forces involved, the administration rushed in and saved our adversaries - Syria, Russia, and the PLO - from certain political and military defeat at the hands of our allies - Israel and Lebanon. Every Druze mortar shell is a deadly reminder of opportunities lost.
The Reagan administration systematically and publicly attacked Israel. Weinberger condemned, Reagan frowned, and State Department Arabists fumed. Instead of focusing attention on the small, incremental steps that could build on the peace process, the administration diluted the climate for peace by advancing a quick fix, dubbed the Reagan Plan. The United States chose the critical moments of opportunity for both Lebanon and Israel to divert attention toward an unachievable, all-encompassing Middle East settlement. This set us apart from our supposed allies while their forces were still in the field.
We pandered to Hussein. He flirted and demurred until even Ronald Reagan must have realized that a Jordanian King cannot be a statesman when he fears assassination for merely talking of peace with Israel. We pandered to the Saudis. They have taken our AWACS, recycled our petrodollars to the PLO, and have continued to undermine the peace process begun at Camp David.
Basically, Ronald Reagan and his administration have frittered away Lebanon's opportunity of a year ago to join Egypt as another nation at peace with Israel. The Reagan Middle East policy has lurched from confusing and ill-timed to vague and dangerous.
What are the broad policy lessons of Lebanon?
* After 35 years of Jordanian and Syrian refusal to negotiate with Israel, the US should stop trying to entice them into the peace process with extravagant promises, sophisticated weapons sales, and a hope that US indecisiveness and weakness will be interpreted as flexibility and ''evenhandedness.''
* For 60 years, Syria has insisted that all of Lebanon is a part of a ''Greater Syria.'' Syria has cast its lot with the Soviets. No carrots offered by the US will induce them to quit Lebanon, particularly with their cherished goal of annexing Lebanon within sight.
* Saudi money and influence is always going to place its highest premium on deflecting radical Arab threats to the monarchy's survival rather than advancing any plans, large or small, for peace in the region.
* Arab states will sign a peace treaty with Israel (as in the case of Egypt), or find a modus vivendi (as in the case of Jordan and Lebanon), when it is in their best interests and when their leaders do not fear assassination by radicals for seeking peace with Israel.
* Unfocused American political intervention can often be counterproductive and downright dangerous. Grandiose ''overall'' settlements make good press conferences, but they also send the wrong signals and can turn the potential for an incremental step toward peace into a major combat imbroglio dragging us closer to a full-scale war in the Middle East.
While it is clear that all of Lebanon's problems cannot be solved by any single event, it is equally clear that the withdrawal of Syria and a lessening of Soviet control is the crawling before the walking, the sine qua non, of the Lebanon equation.
What then should we do now?
First, we must prevent the collapse of the pro-Western Gemayel government, if for no other reason than that it would be interpreted as an instant American debacle. Congress must make it clear that our military presence is neither an open-ended blank check nor a face-saving exercise of such short duration as to constitute merely a ''decent interval'' before Syrian forces and their radical proxies march into Beirut.
Second, the Gemayel government must be persuaded to negotiate a genuine rapproachement with those Lebanese elements patriotic enough to reject Syrian collaboration and Russian domination. Obviously, much will depend on our ability to convince the Lebanese that our treatment of Israel over the past year will not be repeated with them at some critical moment.
Finally, the US must recognize that only effectively coordinated US-Israeli efforts will be successful in deterring Soviet-Syrian designs in Lebanon and throughout the Middle East. It is time for a new strategic agreement between us and our democratic ally, Israel. The US must make it clear to Syria, Jordan, Saudi Arabia, and the USSR that continued intransigence will result in stronger American support for Israel and, ultimately, for Israeli claims in the Golan, Gaza, and the West Bank.
With dependable American support and a consistent Middle East policy, Israel and moderate Arabs can be brought together by time and self-interest in an accommodation indistinguishable from peace. Israel and Egypt do not have a perfect relationship, but Israelis and Egyptians are not killing each other, either. Reproducing this situation within Lebanon would be a significant contribution to peace.