Sharing risks and costs of military alliance : burdens of peace and war -- Case one: The multinational force in Lebanon, 1982-1984 : national collective action -- Case two: The Persian Gulf in 1990-1991 : leadership and legitimacy -- Case three: The Balkans : incubators of European insecurity -- Case four: NATO and Afghanistan : coalition warfighting and stability operations in a new century -- Case five: Nuclear abolition and arms reduction : stakes and risks for NATO.