On 10 April the most senior home-based Ustaša , Slavko Kvaternik , took control of the police in Zagreb and in a radio broadcast that day proclaimed the formation of the Independent State of Croatia ( Nezavisna Država Hrvatska , NDH ) .
On April 10 the most senior home-based Ustaša , Slavko Kvaternik , took control of the police in Zagreb and in a radio broadcast that day proclaimed the formation of the Independent State of Croatia ( Nezavisna Država Hrvatska , NDH ) .