The predominant conception of international aid remains anchored in a dualistic vision of the world: a 'North' considered wealthy and developed comes to the rescue of a poor and under-developed 'South'. The 'civilizing' missions that justified 19th-century imperialism were substituted by themes - such as 'third world-ism' and development aid - of the second half of the 20th century. After the Biafra war, defence of fundamental human rights begins to justify claims to the 'right to intervene' as practised by nongovernmental organizations, such as Doctors without Borders, setting the tone for what humanitarian action should be.