Last July, four high-ranking tech executives — all of them involved with artificial intelligence — were sworn into the US Army Reserves with the rank of lieutenant colonel. They were part of a new unit called Detachment 201, also known as the Executive Innovation Corps. The Pentagon has introduced many initiatives to deepen relationships with Silicon Valley. But making officers out of multimillionaire executives with no military experience served as a strong symbol of a new era in which venture capitalists and technologists see themselves as essential to the defense of the nation. The tech industry, which once prided itself...