CAN ONE hope that Lebanon will be the better for Syria's sudden complete victory over Gen. Michel Aoun? Leader of a defiantly nationalistic Christian faction, he had holed up in the heartland to fend off the powerfully armed Syrians and a Christian-led, Syrian-supported Lebanese government eager to extend its authority over the whole country. With his collapse, the chances of success are materially improved.

The Lebanese government of Elias Hrawi that Gen. Aoun opposed was indeed installed under Syrian auspices. But it was invented under broad Arab auspices at Taif in Saudi Arabia a year ago, and it has already taken the crucial legitimizing step of abandoning the old unbalanced favor for the Christian minority and providing for parliamentary equality (once elections can be held) between the Christian and Moslem communities. The threat of force is old hat in Lebanon, but the employment of force in the name of national fairness is something new.

This latest Syrian power play marks the first application in Lebanon of the Middle East configuration created by the Gulf crisis. As Syria backed President Hrawi, Iraq armed Gen. Aoun: their proxy war, arising from Syria's support of Iran against Iraq, had been a part of the Lebanese scene for some time. But Syria's new move in Lebanon plainly came out of its larger decision to join the American-led squeeze on Iraq. Presumably, Damascus believed that Iraq's isolation made the time right. It set up an economic blockade of the Aoun enclave two weeks ago. The weekend military assault finished the job.

The United States is keen not to be seen paying off Damascus for its Gulf role by giving a green light to a Syrian attack in Lebanon. It is nervous about any development there that could jostle its Gulf hand. But Washington knows the importance to Damascus of ending Syria's frustration in Lebanon, and it is on record supporting the stated Syrian-Lebanese purpose of bringing Gen. Aoun out of military defiance and into the political processes of a united Lebanon. Reconciliation, not vengeance, remains the goal the United States must support over all others.