Among those being mentioned for Trump’s defense secretary are Christopher Miller, who served temporarily during his administration, Michael Flynn and Mike Pompeo. WASHINGTON — Donald Trump is sparking fears among those who understand the inner workings of the Pentagon that he would convert the nonpartisan U.S. military into the muscular arm of his political agenda as he makes comments about dictatorship and devalues the checks and balances that underpin the nation’s two-century-old democracy. A circle of appointees independent of Trump’s political operation steered him away from ideas that would have pushed the limits of presidential power in his last term,...