 By 1972 there was growing pressure from other commanders , particularly Kaúlza de Arriaga 's second in command , General Francisco da Costa <unk> , for the use of African soldiers in Flechas units . Flechas units ( Arrows ) were also employed in Angola and were units under the command of the Portuguese PIDE . <unk> of local tribesmen , the units specialised in tracking , reconnaissance and anti @-@ terrorist operations . 
