The trucks that crashed into the US Marine compound and French paratrooper barracks in Lebanon, exploded, and killed several score servicemen this weekend, enacted a tragic event that had been feared.
The loss of so many ''peacekeeping'' troops - from the start one of the risks their governments took in putting the multinational force there - is cause enough for sorrow. It comes at a moment when Western policy, and most notably American policy, was again groping for some way to end Lebanon's strife. And it comes at a time the White House was trying to lay out a foreign policy agenda that would survive the rigors of next year's domestic political campaign.
The troops in Lebanon from the beginning were not so much peacekeepers as time-buyers. Physically they were vulnerable to terrorist action. When the servicemen were being shot one by one, warnings that the Marines would be allowed to defend themselves perhaps would do for appearance's sake. But the weekend tragedy underscores what should have been clear all along, that time is shorter for new solutions to take hold than the governments would have had others believe.
For President Reagan, yesterday's Lebanon atrocity sharpens a debate that has been raging within his inner circles: Does he have the leadership involvement, impetus, and machinery to deal with the foreign policy challenges of his final first-term year, made more difficult by the domestic pressures of a presidential campaign?
The President has tried to conduct foreign policy - which is impacted by events and holds no regular timetable - with a staff structure and personal style better suited to domestic policy, which is usually free of surprise and crisis. He prefers to have policy options perk up through his staff, to make decisions on his own time and in the Oval Office. We have seen this again and again on the budget, defense spending, and other domestic issues. It was a pattern that had served Reagan well in his California governor days. He likes to wait out his opposition, to force adversaries to come to him to cut a deal.
But foreign policy involves uncontrollable demands. Mr. Reagan may have to take a more direct, personal role in seeking solutions. Oval Office armchair diplomacy can not adequately anticipate what the White House cannot control.
Lebanon isn't the only potential flashpoint in Mr. Reagan's foreign policy world. Arms protests in West Germany and elsewhere in Europe this weekend, while attracting fewer demonstrators than forecast, still turned out vast crowds. The millions who protested indicate the potential for deepening unrest over arms deployment and for escalating demands to end the arms race. Central American leaders warned again this weekend that too much interference in the region is raising the risks of war.
Some of Mr. Reagan's political operatives are deeply concerned about his foreign policy standing. They attribute his recent rise in the polls to the economic recovery. The public disapproves of his handling of foreign policy - particularly in Central America and Lebanon. They worry that the two regions could become Vietnam-like quagmires.
But President Reagan himself does not appear to share the sense of urgency that troubles his aides. His diffidence about running again, pushing back a hard decision possibly to early February, is of a piece with his patience toward his initiatives abroad. He displays no great hurry to take personal charge of negotiations, no signal he thinks his policies are amiss or his time for action short.
In the Middle East, even before the truck-bomb tragedy, Mr. Reagan had to go back to the drawing board. His current goals - ensuring a cohesive Lebanese government, Israeli withdrawl, and Syrian withdrawal - were not his first goals. One proposal now is to build long-range ties to Syria, offering the Syrians incentives to end their troublemaking role. Mr. Reagan's first reaction to the terrorist act was to dig in and assert there would be no marine pullout. Nonetheless, the administration will be forced to reevaluate the marine presence.
Mr. Reagan will travel to Asia early next month, to China next spring. These are the highlights of his foreign policy calendar. A summit with Yuri Andropov - the one event that could give him a major foreign relations lift - appears hostage to Soviet willingness to make a significant arms limitations deal.
What we see, in other words, is a President largely content with the policies he ran on in 1980 as they have evolved under the pressure of events to date, and with the leadership style that gave him his domestic policy successes. His two general election goals for world affairs - redressing the decline of American military power and overcoming the Vietnam syndrome - have endured.
While acknowledging the administration's view that it cannot control all the world's competing demands, we trust yesterday's tragedy will alert the White House to the dangers of a static policy in the Middle East.