NEW BATTLES in Lebanon, new waves of refugees: two things are going on. The Israelis, long cursed for entering and staying so long, are leaving, but are leaving behind a vacuum the contending Lebanese tribes are struggling to fill. The Syrians, having outlasted all of Lebanon's would-be foreign patrons (French, American, Israeli), are imposing an order of their own, but only slowly and partially. Between Israel's withdrawal and Syria's hesitation, Lebanon bleeds and fragments.

At this point in the withdrawal, Israel has no energy left to serve the purpose -- manipulating the large affairs of Lebanon -- which successive governments in Jerusalem pursued by political and military means from the mid-1970s on. Those Lebanese, mostly Maronite Christians, who bet on Israel are paying dearly for it. Only in the swath of southern Lebanon closest to their border do Israelis expect to exercise concern -- a concern limited to border safety. They will rely mostly, and tacitly, on the awakened Shia community to keep the enfeebled PLO from forming up again.

The broad Syrian purpose is to dominate Lebanon -- for considerations of security and Syrian and Arab politics alike. The particular Syrian purpose is to wipe out the gains made after the Israeli invasion of 1982 by Lebanese elements not subordinate to Damascus. This explains why the Shia and Druze are on the march in the south and in Beirut and why the Christians are on the run. Those on the march are, as usual, going too far. The Syrians could use their influence to reduce the pain -- specifically, to defuse the confrontation building around Jezzin. The fate of tens of thousands of Lebanese (and much else in Lebanon) depends on whether they will actually assert the imperial authority they claim.

One hears much about Lebanon's tribes and warlords these days and little about its government. The Christian president faces a rebellion by a well- armed Christian militia leader claiming that he has bowed excessively to Syria. The Sunni Moslem prime minister resigned in April. The United States, badly burned, transmits good wishes cautiously from the sideline. It should keep a brighter spotlight on the bloodshed and upheaval, and it should funnel more humanitarian aid through the lone custodian, frail as it is, of the idea of Lebanon -- the Lebanese government.