On 14 March 2012 the International Criminal Court delivered its long awaited first judgment in the case of Thomas Lubanga Dyilo. The accused was convicted of committing, as co-perpetrator, war crimes consisting of enlisting and conscripting of children under the age of 15 years and using them to participate actively in hostilities in the context of an armed conflict not of an international character. The article critically analyzes the Court’s reasoning with regard to some crucial issues pertaining the definition of the crimes, such as the nature of the armed conflict where they have been committed and the legal characterization of the relevant conducts. The analysis is conducted with the view to assess the impact of the conclusions reached by the Court on the progressive development of international criminal and humanitarian law.