NATO enlargement has been called the first major crisis in Russian-Western relations since the Cold War ended. What is it all about?

"Enlargement" is a proposal to accept three to five members of the former Warsaw Pact into NATO. This would bring the western boundaries of the alliance closer to Russia. The "Vizegrad countries" - Poland, the Czech Republic, Hungary and Slovakia - are the likely initial candidates.

Stalin's defensive belt of states from the Baltic to the Black Sea unravelled with the demise of the Warsaw Pact. It remained a passive buffer, dividing Europe. Those states now seem likely to come under the umbrella of NATO, the Cold War victor.

It is bitter for Russia to see that the peoples involved want to join NATO. They should be convinced communists by now, after 50 years of indoctrination. But the future of communism was destroyed by economic failure and by the ruthless, limited men who professed to be building it.

Seamus Martin has described Russia's genuine military concerns, rooted in history and sharpened by the disintegration of its once-great army.

Since 1993, enlargement has been thoroughly debated in the military and diplomatic journals. One has to admire the quality of the arguments, especially in the Journal of the International Institute for Strategic Studies (1155).

Why enlarge? The reasons given are rather cloudy. They included helping stability in East-Central Europe (ECE), where many wars have originated, and an attempt to, integrate still-divided Europe, including isolated Russia.

The reasons given indicate considerable vision and a desire to head off future causes of strife. There is also the often unstated need to find reasons for NATO's continuance. It was set up "To safeguard the freedom, common heritage and civilisation of its peoples... founded on the principles of democracy, individual liberty and the rule of law... to promote stability and well-being in the North Atlantic Area... and for collective defence."

It has succeeded. Why not wind up or let it wither? The answer no NATO, no US. No country in the alliance wants a Fortress America. Furthermore, the institutions, procedures, rules and compromises so painfully developed cannot be lightly dismantled. NATO) the saying goes, was built "to keep the Americans in, the Germans down and the Russians out".

There is the conviction that institutions either go forward or wither. Sir Roger Palin has said that the need to find a "broader rationale for NATO's existence amid the disintegration of its erstwhile adversaries" is a reason for its involvement in peacekeeping.

Simon Jenkins in the Times of London rubbished enlargement. He called it "a classic case of international fidgeting". Good knock-about stuff - but hardly constructive.

Jenkins does make an important point that must preoccupy some Poles and Czechs: "In July, Britain will sign a guarantee that I believe it does not mean to honour - covering precisely the region where it dishonoured one 60 years ago.

Well, dishonoured two, actually. Hope triumphs over experience if the Polish people wish to join NATO. Britain and France made no attempt to fulfil guarantees given to Poland, Romania and Yugoslavia before the second World War. "Little more than anti-fascist slogans shouted into the wind," one historian said. Poland was ignored in September 1939.

Yalta and the failure of the "Grand Alliance" to support the 1944 Warsaw Rising should also have taught the Poles about trusting great statesmen.

Poles are victims of geography; they know what 45 years of Russian hegemony mean. They may reckon that Americans lack the aplomb - and the subservient press - to let a Sarajevo be shelled daily for three years and four months without reply.

The three "nos" of NATO's December 1966 statement - that the alliance has "no intention, no plan and no reason" to put nuclear weapons into the new countries may reduce Russian concerns. Foreign troops will also stay out. Whether NATO will forego troop and nuclear stationing, under all circumstances, in the special charter proposed by the US Secretary of State, is not clear.

Article 5 of the NATO Treaty says that an armed attack on one member is an attack on all and will be responded to accordingly. This means extending the nuclear umbrella over the new members. The number of nuclear weapons in Europe has been greatly reduced. The Russians may fear attacks on their strategic weapons by aircraft from Polish airfields.

Opponents of enlargement say, with some truth, that the Vizegrad countries are already stable. The prospect of EC membership has ensured good behaviour. Minority rights and civilian control of their militaries are firm. Furthermore, the Russians forces are incapable of attacking them.

However, a former Polish Minister for Defence has said: "The key reason we want to be in NATO is to secure our own democracies. We need to keep down in our country the very same kind of nationalists Yeltsin is contending with, the same kind that destroyed Yugoslavia."

The advocates of enlargement are convincing and flexible. As the issues clarified, it became obvious that enlarging the alliance without an equal effort to improve relations with Russia could have serious consequences. Ms Albright's surprise offer of a joint NATO-Russian brigade and the proposal for a new Atlantic Partnership Council are efforts in that direction. Perhaps Russia's opposition is an attempt to extract the best terms possible in return for accepting changes that cannot be halted.

The reintegration of France into the NATO military system looks? uncertain. The dispute over command in the Mediterranean has escalated to presidential level in France and the US. France has been out of the loop for 30 years.

Enlargement is being mentioned as a second chance for NATO to prove itself. The extraordinary inaction in Sarajevo and the demands for American troops caused more Anglo-American tension than became public at the time. People were dying daily while NATO aircraft stood expensively idle on Italian airfields. The very credibility of NATO came into question before air action was finally launched. The Sarajevo guns fell silent almost immediately. Scapegoating the UN seems less prevalent among well-informed people.

There is scepticism, especially in Britain, about enlargement, but it seems that the alliance accepts it. NATO generals must look appalled at Poland's long borders and hope that the Russian army does not reform too soon. Ratification by 16 member parliaments will take time. But Ms Albright has done her homework thoroughly. The long debate is over. Someone has said that enlargement is a bad idea whose time has come...?