Niger's political history has lacked a synthesis on the army's involvement in politics since independence. The country is a fertile ground for such analysis. Between 1964 and 1999, the country witnessed three successful military coups during the democratisation process (April 1974, January 1996, and April 1999) and at least four military coup attempts (1964, 1975, 1976, 1983). In its forty years of independence, Niger has been under military rule for twenty-one years. It has also experienced seven different institutional regimes while four out of the six presidents who headed the country were soldiers. Niger evolved from the Second to the Fifth Republic in less than ten years - from the national conference (November 1991) to the last military coup (April 1999). In statistical terms, Niger has been witnessing a military coup or a military coup attempt every five-years since 1974. In addition to that, the country recorded seven mutinies and various other forms of troop rebellion between December 1963 and August 2000. In terms of institutional instability, Niger's record is unparalleled in Africa. A study on the army is therefore more needed than ever before. The recurrence with which the military appears on the political scene imposes another way of looking at Niger's army. A critical analysis of the military phenomenon, if not an assessment, would help envisage new prospects for Niger's future. This work, which was undertaken by a multi disciplinary team, suggests an analysis, from a historical and sociological perspective, of the long-standing involvement of the army in politics (the apparition of war leaders in the 19th century, the transition from colonial army to national army, the politicisation of the army and the emergence of 'military-politicians', the army sociology.). It aims at providing an answer to a key question: Why is the army so deeply involved in politics in Niger? It reveals how a significant military component has been gradually built up in Niger's political arena to become a highly dynamic political entrepreneur, able to compete with civilian politicians. The work shows, on the one hand, the significance of socio-political and economic contexts that promote the propensity for military interventionism, and on the other hand the transformations within the army that explain its propensity to intervene. It relates two decades of 'military rule', analyses their modes of legitimating, organising and managing power, gives an assessment of their economic policies and sheds light on women's role in that institution, which was thus far a men's business.