President Trump’s vision of soldiers marching and tanks rolling down the boulevards of Washington is moving closer to reality in the Pentagon and White House, where officials say they have begun to plan a grand military parade later this year showcasing the might of America’s armed forces. Trump has long mused publicly and privately about wanting such a parade, but a Jan. 18 meeting between Trump and top generals in the Pentagon’s tank — a room reserved for top secret discussions — marked a tipping point, according to two officials briefed on the planning. Surrounded by the military’s highest ranking...