| Defense Department technology chief Emil Michael, best known as Uber’s No. 2 executive in the 2010s, is one of several Pentagon leaders who have embraced a Silicon Valley ethos and an investor’s tool kit. The approach has sparked a frenzy among defense tech firms, as well as concerns from others that presidential appointees may be ushering in their chosen firms and taking on risks with taxpayer dollars — while placing fewer guardrails on new technology. | 
