The United States already spends more on the military than the next seven countries combined, and maintains the most advanced fighting force in the world. For nearly a decade after Sept. 11, the Pentagon had a virtual blank check, receiving an 11 percent increase in 2002 and a 10 percent increase in 2008, according to the Center for Strategic and International Studies. President Barack Obama’s proposed increase for the 2018 fiscal year, at 6 percent, was already excessive, and now Mr. Trump has gone significantly higher.

While he argued in a speech on Friday for making “one of the greatest military buildups in American history,” Mr. Trump has offered no coherent case for more money or how it would be spent. Certainly, he hasn’t suggested that the United States should prosecute another war, having talked broadly about avoiding new conflicts and retreating from international leadership.

Yet, experts say the $54 billion increase, which he is expected to unveil formally in a speech to Congress on Tuesday night, could only be justified by a whole new level of force deployment in regions where the American military presence is relatively limited. One administration official said Mr. Trump’s request would include more money for new ships and aircraft and for establishing a “robust presence in key international waterways and choke points,” like the Straits of Hormuz and the South China Sea, Reuters reported. This appears at odds with Mr. Trump’s rhetoric about prompting allies to take more responsibility for defending themselves while America focuses on securing its own borders.

Mr. Trump’s plan, administration officials say, would impose spending cuts on nondefense programs — while sparing Social Security and Medicare from any cuts — to pay for the gigantic Pentagon increase. That’s a choice that would harm millions of Americans while shoveling more profits to military contractors.