Brussels — When Greece let the second shoe drop at the NATO defense ministers meeting in Brussels Dec. 8, the bang wasn't as loud as its NATO allies had feared. But the thump was still noticeable.
Greece is not leaving the military wing of NATO after all, according to Greek sources. It is not closing American bases in Greece. And, after strong American objections, it is not ''vetoing'' Spain's entry into NATO. Nor is it opposing the NATO-approved US negotiating position of ''zero option'' in the Geneva talks on European nuclear arms control.
Greece is, however, asserting national control over the bulk of its forces in peacetime. It is rejecting establishment of a new NATO headquarters in Greece, of an overlapping flight information district with Turkey, and joint Greek-Turkish control of the Aegean Sea. All these were points in the agreement worked out by NATO commander Bernard Rogers for Greek military reintegration into NATO last year after a six-year absence.
The Greek position on withdrawal from NATO and closure of American bases had been ambiguous prior to Greek Prime Minister and Defense Minister Andreas Papandreou's presentation in restricted session at the NATO defense ministers meeting Dec. 8. In his fall election campaign Papandreou had advocated both actions. In private contacts with European governments he had been more moderate , but it was not clear which line would prevail.
Papandreou dramatized his demands by not appearing at the traditional Eurogroup meeting Dec. 7 that opened the week of NATO's winter ministerial consultations - and by blocking the Eurogroup's final communique by a day.
According to Greek sources, however, Athens is not making its continued membership in NATO conditional on meeting of its demands. It expects negotiations on the issues, and it expects them to last a long time. The demands include: a NATO guarantee of Greece's border with Turkey and American military aid to Greece that is proportional to aid to Turkey. The Greeks also call for withdrawal of all foreign troops from Cyprus.
On frontier guarantees the Greek sources indicated Athens might be satisfied with a general NATO declaration saying all member states agree not to use force against the other. Turkey reportedly opposes this, however.
NATO sources interpret Papandreou's position at Brussels as an attempt to moderate the substance if not the rhetoric of the anti-NATO, anti-American campaign that helped sweep him into office a few months ago.
The sources suggest this is a sensible transformation of a vocal out-of-office candidate into a prime minister with the responsibilities of power. They find trimming of Greek demands in line with national interests; Greece's last withdrawal from the military function of NATO from 1974 to 1980, they note, served only to cut off NATO's considerable infrastructure aid for Greece and to leave Turkey as the only Balkan voice inside NATO.
For Greece, Spain's membership in NATO was an issue separate from anti-Turk, anti-American, or anti-NATO considerations. Papandreou had intimated that Greece might not sign the protocol for Spanish entry out of solidarity with the Spanish socialists.
The Americans told the Greeks, however, according to US sources, that such use of a ''veto'' - since Spain would not formally apply for membership unless all NATO governments signed on - was unacceptable.
On issues relating to Turkey, Greece's hand is weak vis-a-vis the US because of American interest in an expanded Turkish role in projecting Western power into the Gulf area. It is not clear how far Turkey would be willing to play this role, since it regards itself as a bridge to the Islamic Middle East.
The military government in Ankara welcomed US Defense Secretary Caspar Weinberger's praise on a visit en route to Brussels, however, along with Weinberger's offer of ''as much assistance as we can'' (give). It especially welcomed his embrace as a contrast to European sanctions in economic aid to Turkey after the jailing of former Turkish Prime Minister Bulent Ecevit.
On US military aid, Greek sources said that Athens seeks an amount that is in some proportion to that granted Turkey.
On the issue of asserting national control over the bulk of Greece's military forces, Greek sources said that one or two divisions might continue to be assigned to NATO in peacetime. But the rest would be oriented toward threats from the ''east'' and ''north.''
NATO's military committee chairman Adm. R. H. Falls says certain disadvantages would follow from a member's committing all its troops to national defense. These would follow from the lack of continual mutual training and sharing of tactical experience.