washington vincent viola army veteran founder high-speed trade firm nominate u.s. president donald trump secretary army withdraw name consideration friday u.s. official say secretary mattis disappoint understand respect mr. viola decision pentagon statement say add secretary defense jim mattis would recommend another candidate soon military time first report news cite viola inability get around defense department rule concern family businesses reason withdraw name viola former chairman new york mercantile exchange leader electronic trade along virtu ceo douglas cifu buy florida panthers national hockey league 2013. trump 's pick army secretary drop