Sentence:  In his submission to the UN, [Christof] Heyns points to the experience of drones. Unmanned aerial vehicles were intended initially only for surveillance, and their use for offensive purposes was prohibited, yet once strategists realised their <WSD>perceived</WSD> advantages as a means of carrying out targeted killings, all objections were swept out of the way. 
Meaning of the word marked with <WSD> tags:  Generally recognized to be true.