MENACHEM BEGIN'S announcement of his intention to resign as Israeli prime minister could be seen coming. After a fiercely strenuous 70 years, he was a battered and--since the death of his wife--melancholy man who acknowledged he could no longer function well. No one more deserves a gentle retirement.

Those of us who have argued vigorously with Mr. Begin's policies should give him his ample due. In the underground he was instrumental in creating Israel and as prime minister he brought it its first peace with an Arab neighbor--high achievements both. But his West Bank annexationist policy has strained Israel's democratic character, diminished the improvement in relations that seemed possible with the Arab world at large and weakened Israel's ties with its foreign friends.

What could change now? The major partners in Mr. Begin's Likud coalition, facing a return to the political wilderness, may be expected to stay together. Having yielded itself to internal feuding, the Labor opposition is poorly placed to test the comforting theory that the Begin years were an aberration and that Israel is overdue to return to a natural liberal accommodationist essence.

Currently it is on the foreign front, in Lebanon, that the downside of the Begin legacy is most evident. In striking all the way to Beirut last year, the prime minister and defense chief Ariel Sharon believed themselves to be creating the conditions for a peaceful repair of long-torn Lebanon. Now Israel, under domestic pressure to reduce casualties, is about to pull part of the way back, leaving Lebanon torn as never before. The United States struggles to limit further damage while Moscow savors the opening to reclaim a regional role. The death of two American Marines in the peacekeeping force in Lebanon only raises the political cost to President Reagan of staying on the Lebanese track.

Mr. Begin, believing it to pose a large and real danger to Israel, worked hard (as did many of his enemies in other lands) to sidetrack Mr. Reagan's plan of last Sept. 1 for a negotiated West Bank peace. We think he was wrong in doing so and that the Reagan plan offered some hope for a safe and stable solution to the conflicts that pose such a wearing and terrible danger to Israel itself.

Mr. Begin's successor will have no reason to question the strength and passion of his commitment to the security of the Jewish state or the fact that he did have some notable achievements in pursuing that security. What that successor should ponder is whether the Begin policy has not by now accomplished everything of usefulness it possibly can and has now turned on itself--and whether it is not time for a change not just of people but of policy as well.