EU diplomats who work in the Justus Lipsius Building in Brussels, the home of the powerful Council of Ministers, have been grumbling lately about a shortage of coffee. By the time we get here in the morning, moaned one official, all these colonels and generals have guzzled it.

It is hard to miss the hundreds of bright-eyed, uniformed army officers who have arrived recently in Brussels' European Quarter. And in the nearby bars and restaurants, conversation is as likely to focus on headline goals and military capability as on tax harmonisation or regional policy.

If this represents a militarisation of the EU, it is a process that is well under way. The EU is creating a 60,000 soldiers that could be deployed as early as next year. In order to provide for circulation of troops, up to four times that number may be required to be on call.

Senior ambassadors from the 15 member-states meet in the Political and Security Committee (PSC) a number of times a week to analyse international developments and plan strategy. The EU Military Committee has been formed to give military advice. And a small but expanding military staff is already in place to command any future operation.

All of these changes have taken place before the ratification of the Nice Treaty. And a rejection of the treaty will not affect them in any significant way.

The treaty has little to say on security matters, apart from granting treaty status to changes that had already been agreed by EU heads of government.

The legal basis for the new military structures and for the Rapid Reaction Force lies in the earlier Treaties of Maastricht and Amsterdam.

The pace of change in the area of EU security policy has been so hectic, however, that it is not surprising the issue of defence should figure so prominently in the referendum campaign.

And even if the Nice Treaty says little on the subject, an annex agreed in Nice by heads of government (but outside the terms of the treaty) outlines in detail how the new military structures should function.

To understand the development of the EU's emerging defence identity, it is necessary to go back a decade, to the start of the Balkan wars.

The shock of such violence so close to the EU's borders prompted some politicians to declare, foolishly, that the hour of Europe had arrived.

Nothing could have been further from the truth, and it soon became evident that Europe did not have the military capability to deal with such a crisis without the help of the United States. After the humiliation of US troops in Somalia in 1991, Washington became more reluctant to send its soldiers abroad on peacekeeping operations.

The crisis in the Balkans also highlighted the way different political, historical and economic interests among EU member-states hindered the formation of coherent EU positions and strategies in moments of crisis.

The EU started to develop its European Security and Defence Identity (ESDI) in the early 1990s; in 1993, the EU decided to give the Western European Union (WEU), western Europe's They are defined in the Treaty of Amsterdam as "humanitarian and rescue tasks, peacekeeping tasks, and tasks of combat forces in crisis management, including peacemaking".

In 1999, however, as the crisis in Kosovo again highlighted Europe's reliance on the US and Washington's reluctance to treat Europe as an equal partner, the EU decided to revise its plans. It decided to adopt the crisis-management and conflict-prevention element itself and, at the Cologne Summit in June 1999, the EU launched the Common European Security and Defence Policy (CESDP).

A summit in Helsinki later that year defined new EU structures to undertake the crisis-management role and proposed an EU Rapid Reaction Force that would be able to deploy up to 60,000 troops within 60 days and sustain them on the ground for at least a year.

The Rapid Reaction Force is not a standing army but draws on existing forces of member-states and some non-EU countries that want to participate. Last November, each member-state promised how many troops and what equipment it would make available to the new force.

Ireland has committed just under 1,000 troops, most of them regular infantry soldiers but some of them Rangers. Five Irish officers serve on the EU Military Staff.

The Minister for Foreign Affairs, Brian Cowen, has compared the Rapid Reaction Force to United Nations peaceRapid Reaction Corps (ARRC), where certain elements of member states' armed forces are earmarked for rapid deployment if the need arises.

No member-state is obliged to take part in any operation, and the Government says it will only provide troops for missions sanctioned by the UN. This is, of course, a political commitment. Nothing in the EU treaties compels Ireland to take part in any operation, but nothing prevents it, either. In this, NATO members in the EU and the four neutral states enjoy equal status.

Although the Rapid Reaction Force's tasks are limited to such operations as conflict prevention, peace-keeping and peace-making, its geographical range has yet to be defined.

Originally, the force's role was expected to be in and around Europe. But planners are increasingly looking farther afield for possible uses of the force. At a recent planning meeting, three mock scenarios were suggested; two of them, Mozambique and East Timor, were not by any definition in and around Europe.

Another issue that remains to be determined is the force's relationship with NATO. As most EU states are NATO members, many of the troops earmarked for the EU force are also NATO troops.

If the EU wants to get involved in an operation alongside NATO, the Rapid Reaction Force will use NATO's planning structure and NATO military assets. If NATO does not wish to get involved, the EU wants access to NATO assets, something Turkey is blocking at present because it wants a greater say in how the EU force is used.

For political and economic reasons, EU leaders have decided against replicating NATO's planning structures.

This means that, in practice, the EU will use NATO structures even if NATO is not involved in an operation.

Regular contacts between the EU and NATO have now been institutionalised, but both organisations will remain autonomous. Any decision to deploy the force rests with the member-states rather than the European institutions.

The Military Committee will provide military advice to the Political and Security Committee, which will act on behalf of the EU member-states. The military staff will run any military operation, but political control will rest with the member-states.

EU leaders are adamant that the Rapid Reaction Force does not represent a European army, a phrase that can mean almost anything.

What is clear is that the EU treaties do not provide for making the force part of a mutual defence pact. And all EU member-states, not only the four neutrals, are determined to retain sovereign control over defence matters.

Nonetheless, the rapid development of Europe's defence identity is likely to have far-reaching consequences for the EU. It will undoubtedly reinforce the drive towards political union by helping to create a coherent, common foreign policy.

The challenge facing Europe's leaders and its citizens is to ensure the new structures are transparent and democratically accountable, and that they are used wisely in the pursuit of peace.