Following Nigeria's independence from Britain in 1960, the country's political life has been marked by debilitating cycles of corruption, instability and military coups. This political volatility, spurred on by regional violence, led to periods of rapid and at times bloody turnover in the nation's top office. Since 1960, 12 different men have ruled Nigeria -- nine of them military leaders and more than half brought to power by coups. The following are profiles of the tumultuous and often brief reigns of those 12 leaders.