In trying to think through the departure of Alexander Haig from the Reagan administration I am struck by the fact that in early 1979 he left service under the Carter administration in time to be eligible for employment in the next administration.
His departure from Carter employment was at his own request. It came after he had had an open disagreement with the Carter White House over the then President's decision to postpone deployment of the neutron bomb. He was asked to stay on; agreed to stay on; then asked to be allowed to leave. He resigned his commission in the US Army, and his job as NATO commander, as of the end of June 1979. During 1980 he considered running for the Republican nomination for the presidency and was occasionally mentioned as a possibility.
In this present case the former general and White House aide to Richard Nixon has again left high office, this time in a manner which makes him appear in the public eye to be more pro-Israel and pro-alliance than is the Reagan administration.
I use the phrase ''makes him appear'' because there may be more appearance than reality in the difference.
The sequence of events gives some support to the assumption of important policy differences. Friday of last week (June 25) was the day of the heaviest and most savage yet Israeli shelling of Palestinian positions in West Beirut. On the previous day, Thursday, Mr. Haig had submitted his resignation to the President. We are told that there had been sharp differences over whether Washington would tell the Israelis that they must stop the killing in Lebanon.
Did he submit his resignation on Thursday because he wanted a ''softer'' policy toward Israel?
Thursday of last week was also a day when a Reagan administration official outlined the procedure for applying economic sanctions against the Soviet Union which will also damage the economic interests of Japan and the West European allies (if the sanctions work) and which have roused a storm of protest among the allies. This was after the Reagan trip to Western Europe during which the allies thought they had been told that the sanctions would be dropped.
Did Mr. Haig resign over the sanctions issue because he felt that it injured the NATO alliance and US relations with Japan?
Mr. Haig himself was told by the President after a working lunch at the White House on Friday that his resignation tendered the previous day was being accepted. And someone that same day must have sent a stiff message of some kind to Israel because the Israeli forces in Lebanon did not resume the fighting on Friday, Saturday or Sunday.
That same afternoon (Friday) Mr. Haig held a news conference at the State Department at which he read the text of his letter of resignation to the President. The text asserted that ''it has become clear to me that the foreign policy on which we embarked together was shifting from that careful course which we laid out.''
Here was a deliberate assertion of differences over policy. But there was neither then nor since a detailed statement about those differences.
In other words, Mr. Haig wants it on the record that there were policy differences, but he does not spell them out. It is merely assumption that one difference was over NATO pol-icy and the other over Israel.
As for the substance of such matters. The White House has appointed George P. Shultz as the successor to Mr. Haig at the State Department. Mr. Shultz is a distinguished economist with strong personal ties to leading figures in West Germany, France and Britain. He is a particular friend of West German Chancellor Helmut Schmidt. He has a solid record of support for the NATO alliance.
Add on this point that the announced policy of sanctions is aimed particularly at blocking the natural gas pipe line which the West Germans and French want, and which they say they intend to have regardless of the Reagan sanctions. Add also that there is doubt whether the sanctions policy can be enforced. The announcement of it pacifies the neo-conservatives who have accused Mr. Haig of betraying their cause by opposing sanctions. It is doubtful that it will make much real difference.
As for Israel. The amount of killing and destruction caused by Israel's invasion of Lebanon had begun to shock the world, including important political elements in Israel itself. Israel, which calls itself a victim of ''terrorists, '' was itself using military terror beyond a level which world opinion could accept. It had to be stopped by a President Reagan whose rhetoric has supported Israel consistently and enthusiastically.
Would Mr. Haig have wanted to allow the killing to go on longer in Lebanon? I doubt it. And will the administration be less considerate of Israel with Mr. Shultz at the State Department? I doubt it. But Mr. Haig will leave high office labeled in the public mind as pro-alliance and pro-Israel. The apparent Haig-administration difference probably exceeds the substance of difference, widely. It could help Haig's political future.