The invasion and occupation of Iraq led by the United States framed world politics in 2003. These events dominated the international agenda both in terms of substance and method.
They set potential precedents for future interventions - and they forced critics of the war to think much more seriously about alternative approaches to international security.
The results of the war have been mixed and unpredictable for the Middle East region and the rest of the world. While few mourn the passing of Saddam Hussein's regime, the consequences of removing him forcibly without the sanction of international law and on the basis of weak or false intelligence about his possession of weapons of mass destruction, have been dangerous for world order and security. The failure to plan for Iraq's post-war reconstruction and the haste with which the US plans to withdraw from Iraq next year without completing that task underline these dangers, notwithstanding the capture of Saddam Hussein.
They can best be overcome by internationalising the occupation under the aegis of the United Nations, giving Iraqis a greater opportunity to restore their sovereignty by democratic means. That is a difficult but not impossible task. If it is undertaken in tandem with a renewed international effort to tackle the Israeli-Palestinian conflict there is a real chance that the Middle East as a whole could emerge positively from the experience.
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Many of the year's debates about the Iraq war revolved around methods of tackling threats to international peace and security rather than their nature and existence. It is commonly agreed that in a more and more globalised world the combination of failed or rogue states, weapons of mass destruction and new terrorist movements constitutes a growing threat to international stability.
Such analyses have been made not only by United States policy-makers, but by those in the European Union and at the United Nations. But how are they best addressed - by unilateral or multilateral action, preventively or pre-emptively, politically and diplomatically or militarily? These are the questions which divide governments and peoples the world over and will continue to do so in 2004.
Iraq became the issue on which transatlantic relations reached their deepest divide since the second World War and it also divided European states and peoples from one another. But behind this issue there is a deeper one - how the rest of the world should relate to the military hegemony of the United States and whether this US administration and its successors can achieve their political objectives alone, in ad hoc coalitions or through more enduring relationships with other states.
This debate concerns Americans just as much as others. While most of them approved of the war against Iraq, a substantial and growing minority was unhappy with it, while a majority prefers a multilateral approach through the United Nations. These facts were often lost sight of during the war and its aftermath. US media are now reflecting them as they are more actively debated going into a presidential election year.
The relationship between US economic, political and military power is also problematic. Military hegemony facilitates economic and political advantage; but it cannot guarantee them - especially not in a world of growing interdependence, in which political and economic power is much more equally balanced than in the military sphere. We are living through a period in which relations between the most developed and powerful parts of the world are being restructured. In the process new patterns of domination and new constellations of power are emerging.
This is most true of Europe, where the enlarging European Union is struggling to find a more coherent way to govern 450 million people in an unprecedented continental experiment and is having to balance itself against US power across a wide range of affairs. Irish people will be able to observe this more closely over the next six months, during the six-month Irish presidency of the EU. The flow of world politics through its agenda will concern many of these major developments.
Another notable theme of the last year, which is set to continue, is the emergence of China as an economic giant with increasing political influence.
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When full account is taken of growing poverty and inequality in many parts of the world it is not difficult to see why these factors, potentially combined with the more newsworthy ones of failing states, terrorism and weapons of mass destruction, are considered greater threats than the traditional geopolitical conflicts which pitted powerful states against one another.
It is a world in which 2.8 billion people in poorer countries still live on less than $2 a day, 1.2 billion of them on less than $1 a day. Inequality as measured by the ratio of average income of the 20 richest countries compared to those of the 20 poorest, has doubled in the last 20 years. One fifth of the world's population lacks access to safe water and an estimated two billion people lack adequate sanitation, leaving them prone to disease and premature death. Environmental degradation continues apace, affecting probably 25 per cent of all cropland, forest and pasture lands since the 1950s.
Facts such as these underlie the more conventional threats to international peace and security. Unless they are tackled in tandem with them, this will remain not only an unjust but an unsafe world. Injustice and instability are intimately linked - not only between states but within them too.